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^"^ MORPHOLOGICAL CHARACTERISTICS OF LEAVES AND STEMS OF SELECTED TEXAS WOODY PLANTS
IN COOPERATION WITH TEXAS AGRICULTURAL EXPERIMENT STATION
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,^^^ UNITED STATES TECHNICAL PREPARED BY (Cyyj) DEPARTMENT OF BULLETIN AGRICULTURAL ^^é^ AGRICULTURE NUMBER 1564 RESEARCH SERVICE
MORPHOLOGICAL CHARACTERISTICS OF LEAVES AND STEMS OF SELECTED TEXAS WOODY PLANTS
IN COOPERATION WITH TEXAS AGRICULTURAL EXPERIMENT STATION
R. E. MEYER, PLANT PHYSIOLOGIST, AGRICULTURAL RESEARCH SERVICE DEPARTMENT OF RANGE SCIENCE, TEXAS A&M UNIVERSITY COLLEGE STATION, TEX. 77843 S. M. MEOLA, RESEARCH ENTOMOLOGIST, AGRICULTURAL RESEARCH SERVICE VETERINARY TOXICOLOGY AND ENTOMOLOGY RESEARCH LABORATORY COLLEGE STATION, TEX. 77840
WASHINGTON, D.C. ISSUED APRIL 1978
UNITED STATES TECHNICAL PREPARED BY DEPARTMENT OF BULLETIN AGRICULTURAL AGRICULTURE NUMBER 1564 RESEARCH SERVICE
ABSTRACT MORPHOLOGICAL CHARACTERISTICS OF LEAVES AND STEMS OF SELECTED TEXAS WOODY PLANTS. R. E. Meyer and S. M. Meola. U.S. Dep. Agrie. Tech. Bull. No. 1564, 200 pp. The morphological characteristics of leaves and stems of some Texas woody plants were studied from 1966 to 1976. Species representative of various plant families, important undesirable brush species, and impor- tant commercial timber species in Texas were selected. Frequencies of stomata were determined on leaves of 103 species of 30 plant families. Although the leaves of most species had stomata only on the lower sur- face, 17 species in the Pinaceae, Palmae, Liliaceae, Amaryllidaceae, Salicaceae, Leguminoseae, Zygophyllaceae, Solonaceae, and Compositae families had stomata on both surfaces. Frequency of stomata varied widely among species; however, species with stomata on both leaf sur- faces averaged 198 on the upper and 243 on the lower surface per mm^ respectively. Species with stomata only on the lower surface averaged 429 per mm-, or about the same frequency as the sum, of those on species with stomata on both surfaces. The leaf surface and leaf and stem tran- sectional characteristics of 72 woody species of 34 plant families were photographed and described. Scanning electron micrographs were pre- pared of both the upper and lower leaf surfaces, and photomicrographs were made to illustrate the histology of the leaf and stem transections. Both the lamina and midrib areas of leaves were photographed. Stem transections included the outer protective layer (epidermis, periderm, or rhytidome), the phloem and cambium region, and the xylem. Of the 64 species, other than members of the Pinaceae, Palmae, Amaryllidaceae, and Cactaceae families, 56 had at least a few trichomes on the leaves. Twenty-six species had a simple periderm, and 38 formed a rhytidome outer covering. The xylem of 28 species was ring-porous, and in 29 the xylem was diffuse-porous (the other 7 being semiring-porous). KEY- WORDS: leaf histology, leaf surfaces, scanning electron microscopy, stem histology, Texas woody plants.
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CONTENTS Page Abstract iii Acknowledgments vi Introduction 1 Materials and methods 2 Species collected 2 Anatomical methods 6 Frequency of stomata 8 Leaf surface and leaf and stem transections 12 Pinaceae 12 Palmae 17 Liliaceae 19 Amaryllidaceae 23 Salicaceae 25 Myricaceae 30 Juglandaceae 32 Corylaceae 39 Fagaceae 46 Ulmaceae 64 Moraceae 72 Berberidaceae 78 Magnoliaceae 81 Lauraceae 83 Hamamelidaceae 87 Platanaceae 90 Rosaceae 93 Leguminosae 100 Zygophyllaceae 115 Rutaceae 120 Anacardiaceae 121 Cyrillaceae 127 Aquifoliaceae 130 Aceraceae 134 Rhamnaceae 142 Tiliaceae 149 Tamaricaceae 151 Cactaceae 154 Cornaceae 160 Ebenaceae 165 Oleaceae 170 Verbenaceae 173 Solonaceae 178 Compositae 181 Glossary 189 Photograph symbol identification list 192
V Page Literature cited 193 Index 199 TABLES 1. Names of Texas woody plant species studied and places and dates collected 3 2. Number and size of stomata on 103 Texas woody plant species ... 9
ACKNOWLEDGMENTS The authors appreciate the assistance and advice received in making this study and in the preparation of the bulletin. Particularly helpful in making the study were Erne Glenn, Elizabeth Norton, Judith Ertel, Karen Eikenberry, Julia Shroeder, Thomas E. Riley, William T. McKelvy, and Cynthia Brown for collecting samples, preparing sides, and processing samples for the scanning electron microscope. Thomas E. Register of Carolina Biological Supply Co., Burlington, N.C., prepared the stem sam- ple of berlandier wolf berry. Walter H. Thames, Jr., provided microscope equipment and advice. Personnel at the Texas A&M Agricultural Informa- tion Office and at Photographic and Visual Aids gave special assistance on photograph preparation. INTRODUCTION This study was undertaken to survey the Also, stomatal counts and pore length measure- leaf and stem characteristics of 72 woody ments were made for 103 woody species in plants in Texas, information that will add to Texas. the understanding of the structure of repre- The leaf transections show the internal struc- sentative woody plants in Texas. The main ture of the various kinds of leaves. To our purpose of our program is to describe the leaf knowledge, there is no other collection of photo- and stem characteristics that influence the ab- graphs as complete as this. Information on sorption and translocation of pesticides, herbi- cuticle thickness and structural characteristics cides in particular. This information should of vascular bundles and laminar regions are also be useful for pathological studies and presented. growth studies, as well as basic botanical Photographs of periderm, phloem, cambium, studies. and xylem areas of mature stems are included. The study was designed to complement the Although much information is available on the information on wood technology presented by wood (xylem) structure of woody species, par- Panshin and de Zeeuw (108)^ and Record (119, ticularly of commercially important forest spe- 120) ; anatomy by Metcalfe and Chalk {97) cies, relatively little information is available and Esau (45); dendrology by Britton (19), on the xylem structure of noncommercial spe- Harlow and Harrar (62), Preston (118), and cies or on periderm, phloem, and cambium ''Silvics of Forest Trees" (169) ; general taxon- structure of either commercial or noncommer- omy by Correll and Johnston (SO), Rickett cial species. Reviews of phloem structure have (122), Vines (171), smd Wills and Irwin been presented by Esau (43, UU). (177) ; plant hairs (168) ; and physiology (46, Vines (171) has described more than 1,200 88, 89, 90, 156, 186, 187). trees, shrubs, and woody vines in the South- west, all of which could not be included here. This study takes advantage of the scanning Therefore, species were selected on the follow- electron microscope, which has the facility of ing basis: (1) those representative of various greater depth of field than the light micro- plant families, (2) those important as unde- scope, to elucidate the surface characteristics sirable brush species, or (3) those important of the leaves (79). However, the scanning elec- as commercial timber species in TJexas. tron microscope has been used to survey all Nomenclature used in this manuscript is parts of the plant (102, 163, 16i). The main largely that of Weed Science (75) for the weed problem was finding fields of view not con- species and most commercially important for- taminated with micro-organisms or foreign est species. Nomenclature of the other species materials. These photos record the various was derived from Correll and Johnston (30), types of surfaces found on these woody plants. Gould (58), and Vines (171). In this bulletin, plant families are arranged according to evolu- 1 Italic numbers in parentheses refer to items in tionary development. Genera and species are "Literature Cited," page 193. arranged alphabetically within plant families. MATERIALS AND METHODS Species Collected pressed, and dried for permanent record of all plants sampled. Most samples were collected Samples of all species were collected in the in the fall of 1966 for stomatal counts, leaf various vegetational areas of Texas (fig. 1) transections, and trunk transections. Most sam- and as described by Godfrey et al. (57) and ples for leaf surface photographs were collect- Gould (58), Common and scientific names and ed in the fall of 1973 and spring of 1974. places of collection of all species are listed in Most species common to the southeastern table 1. Twigs with leaves were collected, (Continued on page 6,)
VEGETATIONAL AREAS OF TEXAS 1. Pineywoods 2. Gulf Prairies and Marshes 3. Post Oak Savannah 4. Blackland Prairies 5. Cross Timbers and Prairies 6. South Texas Plains 7. Edwards Plateau 8. Rolling Plains 9. High Plains 10. Trans-Pecos Mountains and Basins
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CO ■+0 i tí CÖ o o CO CO ití ö tí o tí ^ ao rtí og n 1 £ o rtí O ^ '^ 1 Ä tí >»rtí « t: OS r2 tí M es es ^-P'íí?««tíbcSSS 'w 9 o o PQ 'Ö«g. s» -^S'il! tí S: TS Sto ^ « Ss.S2 es es tí ^ 0) < 0) ^ 0 o ^ V OS ^ tí tí 'Sw ^»Tí o O) ^ft^AîQ bû^<Îo ^1 es -(-> CQ 03 ^ 03 ft be 3 S bCÄ o Xi « ^ ^ ^ s OS OS TS o • • 0) OS es • • flS • 'Ö fe os 0) • g os od « o o o o o o o o ^ o o OS o es O o o O ft o PQ Q I QÖÖÖ g p o p o >jfe pq W fe « ^ 0) _ o îrt ^ rt o forests in the Pineywoods were collected near sectioned 8 to 15 /xm thick, and stained in Warren at the Texas State Forest No. 4, near safranin (30 minutes) and fast green (3 to 5 Ratcliff in the Davy Crockett National Forest, minutes). or near Livingston. The Livingston samples Stomatal counts were made on leaves of 103 were collected either at a roadside park about species that had been either permanently 2 miles west or in a forest site about 8 miles pressed or fixed in the Craf solution. Counts east of town. Also, a few samples were col- were made on the upper and lower lamina lected near Crockett, Fred, and Woodville. surfaces of five areas on at least three leaves Species of the Post Oak Savannah area were or leaflets. Areas near the middle of the leaf collected within 50 miles of College Station or leaflet were used for the counts. Counts near Benchley, Bryan, Caldwell, Carlos, Col- were made either from plastic stripped from lege Station, or Washington. Species of the rubber prints {ISJi) or from plastic stripped Edwards Plateau area were collected either directly from the leaves {135) using a rec- near Marble Falls at the Joe Fry or Fred Hor- tangular reticle in the ocular of a microscope. len ranches or near Llano on the Ann Etta Hall Overall and pore lengths of 20 stomata of each Pecan Ranch. species were measured. Species from the South Texas Plains were Several leaves from each species collected in collected on roadsides near Beeville, Campbell- 1966 were placed in water and ultimately used ton, Goliad, Kenedy, Pettus, or Tilden. Cal- for upper and lower surface photographs em- vin Newton collected coyotillo near Uvalde. ploying an overhead Leitz Ultrapak attach- Species from the Trans-Pecos Mountains and ment. Lack of depth of field limited the value Basins area were collected by various people. of most of these photographs. However, a few We collected creosotebush and tarbush from are presented to show the surface of intact Iraan. P. W. Jacoby collected tarbush from leaves. Fort Stockton. Tom Allen collected lechuguilla In 1973, the scanning electron microscope agave about 70 miles south of Marathon. Sand (SEM) became available. It has the capability sagebrush was collected in the Rolling Plains of much greater depth of field and higher by Roy V. Miller and Bobby J. Ragsdale near magnifications than the light microscope. Con- Vernon and Justiceburg, respectively. sequently, in the fall of 1973 and spring of 1974 more leaves were collected for the species Anatomical Methods to be photographed. Samples for leaf and stem transections were Leaf tissues for SEM evaluation were fixed collected from two or more trees mostly in in an aqueous solution containing 4 % gluteral- 1966. Several typical leaves, free of injury and dehyde (volume/volume) and 2% paraformal- disease, were chosen. Pieces to be embedded dehyde (volume/volume) for at least 24 hours. were taken from the midrib and adjoining The samples were placed immediately on ice, lamina from the middle of the leaf or and then, as soon as possible, placed in a re- midleaflet. frigerator (5"* C). Then 4-mm-square pieces Stem samples were collected within 6 dm of of the fixed leaf lamina area were placed in the soil level on mature plants. Horizonal cuts an aqueous phosphate buffer solution (0.1 M were sawed about 13 mm apart in the trunk Na2HPO4+0.1 M NaH2P04, pH 7.3) and held at deep enough to include two or more xylem 5° C. Generally within a week after collection growth rings. The sections then were chipped and fixation, the samples were immersed for out using a hammer and chisel. at least 8 hours in an aqueous postfixative con- The leaves and stem pieces for transections taining 1% osmium tetroxide (volume/vol- of 72 species were fixed in a Craf solution ume) . The postfixed tissues were subsequently containing 30 parts 1% chromium trioxide dehydrated with ethanol and then acetone. ( weight/volume ), 3 parts glacial acetic acid, Finally they were dried with a Dentón model 10 parts 40% formalin (volume/volume), and DCP-1 critical-point drying apparatus, using 57 parts water. The samples were subsequently liquid CO2, and stored in a dessicator at room dehydrated in ethanol and tertiary butyl al- temperature. cohol, embedded in Paraplast (m.p. 56°-58° C), Leaf pieces were mounted on aluminum stubs 6 with silver paint so that some upper and lower Cambridge S-4 Stereoscan scanning electron surfaces were exposed. The leaf samples were microscope and viewed at 10 kV. Most sample then coated with gold using a Dentón DV-515 images were magnified 100 to 600 times and vacuum evaporator. photographed with 4- by 5-inch Polaroid film The stubs and leaf pieces were placed in a that produced a negative as well as a positive. FREQUENCY OF STOMATA The frequencies of stomata, overall guard 641 per mm^ in bitter nut hickory. Other work- cell length, and pore length on the leaf surfaces ers found the overall stomata length to be 17, of 103 woody species of Texas are recorded in 20, 23, and 24 /xm long in bitternut hickory, table 2. Frequencies found by other workers pecan, shagbark hickory, and mockernut hick- are also included. ory (H9), In the Corylaceae, the stomatal fre- In eastern redcedar, rows of stomata occur quency in river birch in this study was higher on the adaxial (inside) surface of most all than reported by Sax (129) ; conversely, the leaves and in about four rows near the mar- frequency reported by Carpenter and Smith gins of older leaves. In the pines, stomata are (2i) for American hornbeam was lower. sunken and lie in rows parallel to the long axis In the Fagaceae, stomatal frequencies varied of the needle, occurring at a frequency range widely from 273 per mm^ in black oak to 1,198 of 67 to 113 per mm^. McLaughlin and Madg- per mm^ in overcup oak. In the Ulmaceae, sto- wick (96) found a lower frequency of stomata matal frequencies varied from 310 per mm.^ in the middle and lower shaded areas of the in granjeno to 785 per mm^ in sugarberry. In loblolly pine canopy than in the upper and the Magnoliaceae, as the stomatal frequency in- more open parts. The long axis of the guard creased from 242 to 578 per mm^, the overall cells lies parallel to the long axis of the leaves stomatal size decreased from 31 to 14 /xm, re- in eastern redcedar and in needles of the pines spectively. In the Rosaceae, stomatal frequen- (138). Stomata are present on both the upper cies varied from 207 to 248 per mm^, except and lower surfaces of leaves of dwarf palmetto, for Macartney rose, which had a higher fre- small soapweed yucca, and lechuguilla, but quency (680 per mm^) of smaller stomata. stomata were present only on the lower sur- In the Leguminosae, all members of the Mi- face of saw greenbrier in the monocotyledonae. mosaceae (guajillo, huisache, catclaw acacia, In eastern cottonwood, Isebrands and Larson blackbrush acacia, and honey mesquite) and (81) reported a higher frequency of stomata one member of the Caesalpiniaceae (retama) on both surfaces (292 on the upper surface) had stomata on both surfaces. The other two than we found. Carpenter and Smith (2i), members of the Caesalpinaceae (eastern red- who made an extensive study on woody plant bud and honey locust) and the one member of stomatal frequency and size, found no stomata the Papilionaceae (mescalbean) only had sto- on the upper surface of black willow, whereas mata on the lower surface. our plants had stomata on both surfaces. Most In creosotebush, we observed fewer stomata of their stomatal-size measurements were simi- on both leaf surfaces than did Ashbe (P), who lar to ours. found 240 and 360 per mm^ on the upper and On most species of plants studied, stomata lower surfaces, respectively. However, Barbour were present only on the lower leaf surface. et al. (12) found about the same number on However, stomata were present on both sur- plants in the field but only 158 per mm^ on faces of members of the Salicaceae (eastern greenhouse plants. They found about the same cottonwood and black willow), some Legumi- frequency of stomata on both surfaces. Along nosae, members of the Zygophyllaceae (creo- with most pines, the stems of both cactus spe- sotebush and guayacan), berlandier wolf berry cies and the leaves of flowering dogwood and of the Solonaceae, and some members of the berlandier wolfberry had stomatal densities of Compositae (willow baccharis and tarbush). fewer than 100 per mm^ In the Juglandaceae, stomatal frequencies Stomatal frequencies were evaluated by plant ranged from 252 per mm- in black walnut to size, location, and leaf type. Plants were divid- 8 TABLE 2.—Number and size of stomata on 103 Texas woody plant species Number of stomata Number of stomata Length (per mm2) (per mm2) on— Family Common name Overall Pore on lower surface Upper Lower (/um) according to surface surface other workers Pinaceae eastern redcedar 206 50 25 Do shortleaf pine 89 130 Do slash pine 67 128 Do longleaf pine 68 125 Do loblolly pine 113 130 75-93 {96), 138-180 (155) Do baldcypress 253 3166 117 Palmae dwarf palmetto 451 462 120 Liliaceae saw greenbrier 0 103 28 20 Do small soapweed yucca . 124 107 130 Amaryllidaceae lechuguilla 24 23 165 Salicaceae eastern cottonwood — 157 144 26 20 346 (81) Do black willow 279 289 20 15 432 (2J^) Myricaceae southern waxmyrtle . • • 0 458 23 10 Juglandaceae bitternut hickory 0 641 22 12 Do pecan 0 638 22 12 Do shagbark hickory 0 393 22 12 349 (2^) Do mockernut hickory 0 268 23 12 240 (2^) Do black walnut 0 252 18 8 256 (^-4), 461 (Ij^) Corylaceae hazel alder 0 480 26 13 Do river birch 0 270 26 13 82 (129) Do American hornbeam • • • 0 485 18 10 234 (2JÍ) Do eastern hophornbeam • • 0 540 18 11 iÇagaceae Allegheny chinquapin • 0 641 20 10 Do American beech 0 408 21 9 693 (2Jí) Do white oak 0 826 19 9 514 (2J^) Do southern red oak 0 1,070 21 12 Do overcup oak 0 1,198 22 11 Do bur oak 0 1,136 20 11 Do blackjack oak 0 583 26 15 Do swamp chestnut oak • • • 0 764 19 10 Do chinquapin oak 0 1,050 18 10 Do water oak 0 620 27 13 Do willow oak 0 640 27 14 723 (182), 156 (2J^) Do post oak 0 754 23 14 424(;g4),693 (182) Do black oak 0 273 24 13 405 (2j^),bS0 (182) Do live oak 0 475 21 13 Ulmaceae sugarberry (sugar 0 785 18 11 hackberry). Do granjeno 0 310 23 14 Do winged elm 0 764 26 18 Do American elm 0 389 33 19 79 (129) y 2S0 (2U) Do cedar elm 0 413 22 11 Moraceae osageorange 0 423 26 14 Do red mulberry 0 155 18 10 155 (2U) Berberidaceae agarito — 0 295 24 14 Magnoliaceae tuliptree 0 242 31 20 240 (Í67), 284 (2U) Do southern magnolia — 0 434 29 14 225 (iöP),255 (2U) Do sweetbay magnolia — 0 578 14 9 1,053 (113) Lauraceae redbay 0 449 20 12 Do sassafras 0 311 18 11 306 (2h) Hamamelidaceae sweetgum 0 207 24 14 224 (2U) Platanaceae American sycamore .. 0 227 30 18 278 (Í4),307 (2h) See footnotes at end of table. TABLE 2.—Number and size of stomata on 103 Texas woody plant species—Continued Number of stomata Number of stomata Length (per mm2) on— (per mm2) Family Common name Overall Pore on lower surface Upper Lower (ixm) according to surface surface other workers Rosaceae parsley hawthorn 0 215 35 18 Do green hawthorn 0 248 40 17 Do black cherry 0 207 27 13 196 (^-4), 364 (U8) Do Macartney rose 0 680 21 10 Leguminosae guajillo 2132 3641 19 12 Do huisache 180 162 19 9 Do catclaw acacia 155 126 21 11 Do blackbrush acacia 583 661 15 10 Do eastern redbud 0 272 18 11 266 (2J!f) Do honeylocust 0 187 26 19 276 {2U) Do retama 215 350 22 17 Do honey mesquite 180 126 28 14 85 (100) Do mescalbean 0 306 26 14 Zygophyllaceae creosotebush 208 187 24 13 208 (i^),360 {9) Do guayacan 283 281 18 8 Rutaceae herculesclub 0 186 36 24 Do colima (lime pricklyash). 0 388 34 18 Meliaceae chinaberry 0 389 26 15 Anacardiaceae shining sumac 0 305 29 15 731 {2JÍ) Do poison ivy 0 210 21 14 Cyrillaceae swamp cyrilla 0 350 29 16 Aquifoliaceae American holly 0 269 28 13 220 (151), 262 (87), 289 (24) Do yaupon •.. 0 351 21 10 Aceraceae boxelder •. 0 475 17 9 Do — i red maple 0 611 19 12 116 (129), 602 (113), 705 (24) Do sugar maple 0 877 12 110 (129) Rhamnaceae Texas colubrina — 0 369 18 10 Do lotebush condalia • • • 0 296 20 11 Do coyotillo 0 589 14 8 Do Carolina buckthorn 0 505 21 9 Tiliaceae American basswood 0 165 23 14 90 (^^),127 (129) Tamaricaceae saltcedar 359 16 9 Cactaceae tasajillo cactus 441 37 18 36 (28) Do Lindheimer pricklypear 421 39 25 35 (28) Cornaceae flowering dogwood 0 54 20 12 83 (24), no (167) Do water túpelo 0 105 27 14 Do blackgum 0 175 26 14 357-376 (113) Sapotaceae gum bumelia 0 404 22 10 Ebenaceae Texas persimmon 0 329 23 14 234-339 (99) Do common persimmon 0 278 20 13 262 (24) Styracaceae Carolina silverbell .... 0 155 22 13 Oleaceae white fringetree 0 165 24 17 T)o white ash 0 310 20 12 30-200 (180), 130 (24) Boraginaceae anaqua 0 700 23 15 Verbenaceae whitebrush 0 251 19 12 Do American beautyberry 0 215 15 7 Solonaceae berlandier wolfberry .. 23 21 10 6 Bignoniaceae northern catalpa 0 405 25 17 Caprifoliaceae rusty blackhaw 0 103 37 20 See footnotes at end of table. 10 TABLE 2.—Number and size of stomata on 108 Texas woody plant species—Continued Number of stomata Number of stomata Length (per mm2) on— (per mm2) Family Common name Overall Pore on lower surface Upper Lower according to surface surface other workers Compositae sand sagebrush 404 15 9 Do willow baccharis Ill 179 39 22 Do tarbush 207 198 26 16 1 Stomatal crypt length. 2 Based on the midrib width; none were present on the lamina. 3 Based on lamina area; few if any were present on the midrib. * Stem branch or pad surface. ed according to height into three categories: amined stomatal frequency variation and con- those over 15 m, 6 to 15 m, and under 6 m tall cluded that (1) stomatal frequency tended to had stomatal frequencies of 466±313, 349±209, be lower the larger the leaf under dry, un- and 316±183 stomata per mm-, respectively. crowded conditions; (2) leaves on the upper Thus, there v^as a tendency for stomatal fre- part of the plant tended to have higher stoma- quency to be directly related to the height of tal frequencies than those toward the base of the plant. The plants found in the moist areas the tree; (3) on individual leaves, frequency of east Texas, semimoist areas of east central tended to increase from the base to the apex Texas, and drier areas of central and south and from the midrib to the margin; (4) fre- Texas had 407±287, 402±235, and 282±176 quencies tended to be higher for trees and stomata per mm^, respectively. Thus, plants shrubs than for ground flora; and (5) frequen- from the drier part of the State tended to be shorter and have a lower frequency of stomata cies tended to be higher for marginally sunlit than those from areas of the State receiving species than for shaded flora. Zucker {188) higher rainfall. has also reviewed factors affecting stomatal In some cases the variations between sto- differentiation. Dunn et al. {í2) found sto- matal frequencies found in this study were matal size varied markedly within a species. markedly different from those in other studies. At least in some species, such as osageorange, In a study in England, Salisbury {127) ex- there were four classes of stomatal sizes. 11 LEAF SURFACE AND LEAF AND STEM TRANSECTIONS Pinaceae is one cell deep, and many cells contain tannin. The thin leaf margin (fig. 2B) is formed by Eastern Redcedar several epidermal cells (fig. 2D). Stomata are {Juniperus virginiana L.) sunken and occur only on the inner surface of Eastern redcedar occurs in the Pineywoods, the sharp-pointed leaves (fig. 2D). Under- Post Oak Savannah, Blackland Prairies, and neath the epidermis on the outer side is a layer Edwards Plateau of Texas {58). An evergreen of fiberlike cells that usually form a continu- tree, generally pyramidally shaped, it rarely ous layer in the terminal leaves (fig. 2D) and attains a height of more than 15 m and a trunk a band spanning the stomata on the older diameter of more than 6 dm in Texas {171). leaves (fig. 2E). Inside, palisade parenchyma lie under the fiber layer. The vascular bundles Leaf shape and surface are generally either wholly or partially sur- The leaves are of two types {63) : terminal rounded by a sheath of spongy parenchyma. juvenile leaves are sharp pointed, spreading, Many cells contain tannin. In the mature leaf glandless, glaucous, 1.3 to 1.9 cm long; mature (fig. 2E), a large resin duct lies under the leaves are scalelike, appressed, overlapping, epidermis opposite from the large central vas- glandular, dark green, acute or obtuse, about cular bundle. The duct is a schizogenous 2 mm long, and four-ranked. Some leaves are intercellular space surrounded by thin-walled, intermediate between the two forms {83, 171). secretory epithelial cells. Both surfaces of the sharp-pointed leaves Stem transection have slight undulations on the epidermis (fig. 2, A, B).2 Stomata occur only on the inner (ad- The sequential development of the stem in axial) surface of the sharp-pointed leaves and the Pinaceae has been discussed by Koch {88). on both the inner and outer surfaces in the In eastern redcedar, the bark is light reddish scalelike leaves (fig. 2C). Stomata occur more brown, brown, or ashy gray, usually about 6 or less in rows with the long axis of the guard mm thick. The outer bark is easily shredded cells parallel to the long axis of the leaf. into long, narrow fibrous strips with fringed Trichomes are absent. edges. The inner bark is light creamy yellow, about 3 mm wide {26). The periderm is com- Leaf transection posed of two to five layers of phellem, a layer Figure 2D shows the opposite or four-ranked of phellogen, and two to five layers of phello- arrangement of the terminal leaves. The leaves derm (fig. 2F). Underneath are two layers of are somewhat crescent shaped and have an en- square, highly lignified sclereids. These tan- tire margin. The opposite leaf arrangement gential sclereid layers occur repeatedly invi^ard, and entire margin are characteristics similar separated by alternate layers of sieve cells and to Rocky Mountain juniper {Juniperus scopu- parenchyma (fig. 2, F, G). The sieve cells are lorum Sarg.) and Juniperus horizontalis square, and the parenchyma are flattened. El- Moench. (5^, 83). A prominent cuticle occurs liptical resin ducts are present both in the inner on the surface of the epidermis; the cuticle is and outer bark regions and are alined more or crystalline on the outer surface of the smaller less in tangential rows. leaves but smoother on the older ones and on The translocating phloem lies outside the the inner surface of all leaves. The epidermis cambium. The thickness is not definite in this section (fig. 2G). Probably no more than the - Lettering on photographs is identified on page 192. volume up to the second fiber layer is active 12 PN-5488 FIGURE 2.—Eastern redcedar {Juniperus virgimana L.). A, Leaf tip outside surface (X 100). B, Adaxial leaf surf ace near tip (X 100). C, Abaxialleaf base (X 120). Z), Small leaf transections {X 216). 18 »7s^ ^ í,.*^¿•^ «*,.*/ -^^ •* -« <,.' .i^"" ' i*j r^-*^/-:^' sm'^ié F 'i ^ ^-5 ■ \ 1 ! H H'i M>^-; PN-5489 FIGURE 2.—Eastern redcedar {Juniperus virginiana L.)—Continued. Í7, Large leaf transeetion (X 167). í", Trunk periderm and outer phloem transection (X 85). G, Trunk phloem, cambium, and outer xylem transection (X 85). H, Trunk xylem transection (X 85). 14 for translocation, because most cells outside ducts lie in the mesophyll, with at least one this area are semicollapsed. on either side of the vascular strand in line The xylem, having a distinctive cedar scent, with the lateral sides of the leaf. Most resin has a thin, nearly white sapwood and a red to ducts are medial, lying about midway between reddish-brown heartwood. The growth rings the hypoderm and endodermis (9Í), Occasion- are distinctly delineated by a band of darker ally one may be found next to the endodermis. late wood (fig. 2H). Tracheids average 20 to Normally two resin ducts are present, but as 35 /xm in diameter, often with intercellular many as four may occur (61). Each resin duct spaces at the corners (63), Parenchyma are is surrounded by 11 or 12 slightly thickened abundant and banded. The rays are uniseriate, epithelial cells. The endodermis consists of a comprised of parenchyma with nodular end single layer of slightly elongated and slightly walls {8U,85,112). thick-walled cells around the vascular strand. Just inside the endodermis are several layers Loblolly Pine (Pinus taeda L.) of thin-walled transfusion cells flanking a pair Loblolly pine occurs in the Pineywoods, Gulf of vascular bundles. The vascular bundles are Prairies and Marshes, and Post Oak Savannah either adjoining or slightly spreading. Figure areas of Texas (58), An evergreen conifer at- 3(7 shows a transection of the three leaves in taining a height of 37 m and a diameter of the sheath area. The mesophyll is rounded and 6 dm, it has a long, clear, cylindrical bole not infolded. The resin ducts lie midway be- topped by an open, irregularly rounded crown tween the endodermis and hypoderm. The (63), The structure of pine is summarized in transfusion tissue is present more or less in detail by Koch (88), radial files. The two vascular bundles are al- most parallel. The transection structure of the Leaf (needle) surface leaves of loblolly pine and various other Pinus In loblolly pine, leaves occur in threes in a species has been reviewed by Shaw (13Jí) and fascicle, lasting 3 to 4 years. They are slightly Sutherland (150). twisted, 13 to 25 cm long, 2 mm wide, glau- Stem transection cous, light to dark green, rigid, with apex sharp, base three sided, and sheath (fascicle) The external bark is reddish brown, rough, about 1.5 to 2 cm long (35, 171), thick, and deeply furrowed into large, coarse, The stomata occur in about 10 rows approxi- appressed scales. It is a rhytidome comprised mately 0.15 mm apart parallel to the long axis of a series of phellogens with their outer phel- of the leaf (fig. 3A), similar to Pinus radiata lem and inner phelloderm cutting off tiers of D. Don (16Jf). The guard cells are recessed in nontranslocating secondary phloem (88). De circular crypts, with the long axis parallel to Vail (39) found that the phellogen area of lob- the length of the leaf. The crypts are often lolly pine was inconspicuous or at most slate filled with wax similar to other conifers (16Í), gray, whereas in longleaf pine (Pinus palustris Shallow lines lie parallel to the long axis of Mill.) and shortleaf pine (Pinus echinxita Mill.) the leaf. The margins are slightly toothed. the phellogen areas are conspicuously ivory Trichomes are absent. white. Figure 3D shows the innermost phel- logen with phellem and phelloderm. Most of Leaf (needle) transection the sieve cells have collapsed, leaving enlarged Figure 3ß shows a transection through the parenchyma and sclereids. The phellem con- midsection of the leaf. The leaf is triangular tains bands of thin-walled cork cells and thick- with an obtuse central angle and a rounded walled sclereids. outer surface (88) similar to other three-needle The inner bark comprises the tissue between pines. The outermost layer is an epidermis the cambium and the innermost phelloderm and covered with cutin. Underneath is the hypo- includes the living secondary phloem.. It aver- derm consisting of two compact layers of thick- ages about 1.5 mm in width. The portion of walled, fiberlike cells that give rigidity to the phloem active in translocating carbohydrates is leaf. The mesophyll are thin walled and either generally only 0.2 to 0.3 mm in width (77), The infolded (fig. 35) or circular (fig. 3C). Resin phloem contains sieve cells, longitudinal par- 15 PN-5490 FIGURE 3.—Loblolly pine {Pinm taeda L.). A, Needle surface {X 120). B, Needle middle transection {X 80). C, Needle base transactions (X 98). D, Trunk periderm and outer phloem transection (X 84). 16 PN-5491 FIGURE 3. Loblolly pine (Pinus taeda L.)—Continued. E, Trunk phloem, cambium, and outer xylem transectlon (X 84). F, Trunk xylem transaction (X 77). enchyma, ray albuminous cells, ray parenchy- The horizontal xylem includes uniseriate, ma, and epithelial cells (fig. ZE). Chang (26) heterogenous, and multiseriate fusiform rays noted that in Pinus sclerenchyma cells were and is composed of ray tracheids, ray paren- absent in the secondary phloem, sieve cells chyma, and epithelial cells. Most rays are uni- often occurred in radial rows of about 10 cells, seriate with ray tracheids at the margins and and albuminous cells were conspicuous at al- ray parenchyma in the middle. The fusiform most every ray section close to the cambial rays are scattered and are usually three or four region. Several other discussions on the cells wide at the midpoint. They contain a resin rhytidome and phloem of conifers are available duct and are comprised of ray tracheids, ray {1,4,5,un. parenchyma, and epithelial cells. The xylem characteristics of loblolly pine have been summarized (32, 76. 88, 108, 112). Palmae The sapwood is white to yellow white. The Dwarf Palmetto xylem (fig. 3F) shows a clear delineation be- tween the early wood and late wood of the pre- [Sabal minor (Jacq.) Pers.] vious year. The longitudinal xylem cells are This palm grows in river bottoms and other comprised of longitudinal tracheids, strand wet places in the Pineywoods, Gulf Prairies tracheids, and epithelial cells. The longitudinal and Marshes, Post Oak Savannah, Blackland tracheids make up more than 90 percent of the Prairies, and flood terraces in ravines of the xylem volume. They are usually round in early Edwards Plateau of Texas. wood and flattened in late wood. Strand tra- cheids occur along the vertical resin ducts. The Leaf shape and surface tracheids have bordered pits {31). Epithelial The dwarf palmetto normally consists of a cells are thin-walled cells that line the resin group of fanlike leaves arising from a crown ducts and secrete oleoresin into them. Longi- on a subterranean rootstock. However, it has tudinal parenchyma are absent {63). been reported to produce a trunk to about 6 m 17 tall {11 ). The leaf has a 3- to 5-dm-long petiole that is rounded below, slightly concave above, and 1.9 to 3.8 cm across. The hastula, a ligule- like extension of the petiole, is prominent, broad, and unequalsided on the upper surface but inconspicuous on the lower surface. On the lower surface, the petiole extends 3.8 to 20.3 cm into the palmate lamina (costa palmate). The lamina is fanlike, 6 to 24 dm in diameter, and either pale green or glaucous. It is folded with a prominent rib at each fold {171). The lamina is divided into about 16 segments, each split two-thirds or more to the base along the upper fold. The lower midribs remain intact. The midrib is recessed on the upper surface and elevated on the lower surface. The laminar segments are 2 to 5 cm wide at the base and taper to a long, unequally two-parted apex. Margins of the laminar segments are generally entire, rarely with threadlike projections. Both of the leaf surfaces (fig. 4, A, B) and the petiole surface (fig. 4C) have stomata in lines parallel to the long axis. According to Tomlinson (162), the long axis of the guard cells runs parallel to the long axis of the lami- nar segments. The stomata are sunken, and the crypts generally are partially filled with wax or cutin. The surface is minutely ridged. Tri- chomes are absent. Leaf transection The leaf is isobilateral. A thick cuticle occurs on both laminar surfaces (fig. 4, D, E). A prominent midrib occurs on the lower fold (fig. 4Ê'). Stomata are limited to intercostal regions (between bundles). The colorless hypodermal cells, just below the epidermis on both surfaces, are one cell deep and are larger than the epi- dermal cells. The hypodermis is interrupted at the substomatal chambers below the stomata. Beneath the hypoderm on both surfaces are several layers of palisadelike parenchyma cells. In the middle are larger isodiametric mesophyll cells. Nonvascular fiber bundles occur about equally below both surfaces. Veins lie mostly in the upper mesophyll. The largest are at- tached by a fibrous buttress to each hypo- dermis; smaller veins usually are joined to the PN-5492 upper hypodermis by a tall fibrous buttress. FIGURE 4.—Dwarf palmetto [Sabal minor (Jacq.) The leaf petiole has one layer of epidermis Pers.]. A, Leaf lamina upper surface (X 240). B, Leaf lamina lower surface (X 220). C, Petiole with frequent sunken stomata (fig. AF). The surface (X 200). hypodermis is two cells deep and is aften inter- 18 rupted below the stomata by parenchyma cells. Fiber bundles without vascular tissue are fre- quent near the periphery, but absent from the central ground tissue of the petiole. Bundles with vascular tissue are uniformly scattered in the central part of the petiole and have large fiber buttresses. The xylem of large vascu- lar bundles usually contains one or two large metaxylem vessels, whereas in small veins the xylem cells are about the same size. The phloem of some large veins is divided into three separate strands, a large lower one and two small strands on each side of the metaxylem vessel {110, 111). Transverse commissures, vas- : \ cular bundles connecting longitudinal veins, are frequent and equidistant from each surface. Liliaceae Saw Greenbrier {Smilax bona-nox L.) Saw greenbrier is a stout, spiny vine with four-angled branches that occurs throughout Texas with the exception of the High Plains and Trans-Pecos Mountains and Basins areas. It either grows along the ground or climbs by tendrils. Greenbrier produces enlarged, spiny underground tubers. Leaf shape and surface The leaf is broad, and unlike most mono- cotyledonous plants, is net veined. The leaf is rigid, simple, alternate, and tardily deciduous; the shape is ovate, cordate, broadly lanceolate, or deltoid; the apex is acute or sharp pointed, the margin entire or with prickles, and the base rounded, truncate, or cordate. The upper surface is smooth and devoid of trichomes (fig. 5A). The lower surface is also smooth (fig. 5B), but contains ranunculaceous stomata (146). The guard cells lie prominently exposed on the surface and are randomly oriented. Leaf transection The leaf has only a thin cuticular layer (fig. 5, C, D). Both the upper and lower epidermal layers are one cell deep with long, flat cells. The palisade parenchyma are two or three cells deep, and the spongy parenchyma are loosely PN-5493 packed, particularly in the lamina (fig. 5C). FIGURE 4.—Dwarf palmetto [Sabal minor (Jacq.) Pers.] Veins lie centrally between the upper and lower —Continued. D, Leaf lamina transection (X 167). surfaces. Philpott (113) found that leaves of E, Leaf midrib transection (X 85). F, Petiole tran- section (X 85). Smilax collected from a shrub-bog site had 19 PN-6494 FIGURE 5.—Saw greenbrier {Smilax bona-nox L.). A, Leaf upper surface {X 220). B, Leaf lower surface (X 220). C, Leaf lamina transection (X 233). D, Leaf midrib transection (X 175). more palisade mesophyll than those from a Both the epidermis and the underlying hypo- mesic mountain site. dermis consist of a single layer of cells. Below in the midrib (fig. 5D), the main vascular are a number of cortical parenchyma with a bundle is surrounded by fibers that in turn are few small vascular bundles occurring in the enclosed in tightly packed parenchyma. Small cortical tissue. Underlying the parenchyma is veins generally have fibers only on the lower an almost complete cylinder of fibers inter- side. rupted only by vascular strands. The main body of the stem consists of vascular bundles Stem transection surrounded by three or four layers of fibers The stem has a marked cuticle (fig. 5E). (fig. 5F). The xylem usually contains two 20 PN-S496 FIGURE 5. Saw greenbrier (Smilax bona-nox L.)—Continued. E, Stem outer edge transaction (X 85). F, Stem inside transection (X 85). metaxylem cells, and the phloem contains 6, A, B). The crypts of the stomata are mostly three or four metaphloem cells. Lignified covered by epidermal lips, usually six {95). parenchyma surround the vascular bundles and The leaf surfaces are slightly undulating from contain starch granules and crystals. the rectangular shape of the epidermal cells, which are elongated parallel to the long axis of Small Soapweed Yucca the leaf. Blunden and Binns {16) found that (Yucca glauca Nutt.) the epidermal cell walls were variably beaded and that most had a prominent surface papilla. Small soapweed yucca, also known as Yucca In this study, a few of the cells had a papilla, angustifolia Pursh. (SO), is a small yucca oc- but none of the cell walls were particularly curring in the Edwards Plateau, Rolling Plains, beaded. The epidermal cells were about the and Trans-Pecos Mountains and Basins areas same size on both the upper and lower surfaces. of Texas. It has a stem usually no more than Blunden and Binns {U), however, found that 0.3 m high and produces a racemose panicle the cell-size ranges varied from plant to plant 0.3 to 1 m tall that flowers in May through and that the cells at the base of the leaf were July. The fruit is a three-valved capsule. longer and narrower than toward the apex. Leaf shape and surface No trichomes were found on the lamina. The leaves are widely radiating, 20 to 90 cm Leaf transection long by 5 to 13 mm wide, narrowly linear with a broader, white, sheathing leaf base, straight, The leaf has an epidermis covered with a concave, stiff, tapering to an apex bearing a smooth thick cuticle. Both the midlamina (fig. spine. The margins roll inward sometimes with 6C) and central lamina (fig. 60) have pali- long shreddy extensions. sade parenchyma, two to four cells deep, inside Both surfaces have submerged stomata ap- both epidermises. The central region of the pearing at random rather than in lines (fig- leaf contains larger spongy parenchyma. Idio- 21 PN-5496 FIGURE 6.—Small soapweed yucca (Yucca glauca Nutt.). -A, Leaf upper surface (X 200). B, Leaf lower surface {X 200). C, Leaf midlamina transeetion (X 98). D, Leaf central lamina transection (X 99). blasts containing bundles of needle-shaped Small vascular bundles are also arranged at the (raphid or acicular) crystals occur in all parts juncture of the palisade and spongy mesophyll. of the mesophyll. Most vascular bundles are enclosed in a sheath Discrete vascular bundles are arranged in of parenchyma. two main arcs, one arc passing across the leaf Large vascular bundles have fiber buttresses (fig. GC) and the second extending only across both above and below the vascular tissue. The the thicker, central part of the leaf (fig. 6Z)). phloem is composed of compact, thin-walled 22 ^>1 ^ ■ SIT' eo ,.. V;;V'^, ''.'./. 'i-'^K^'ï/ 4 • PN-5497 FIGURE 6.—Small soapweed yucca {Yucca glauca Nutt.)—Continued. E, Outer stem transection (X 41). F, Inner stem transection (X 41). sieve tissue. Above the phloem are successive abundant in many parenchyma cells throughout layers of lignified tracheids and xylem paren- the stem. chyma. The small vascular bundles vary widely, with some having many fibers, whereas others Amaryllidaceae have only a few fibers on the inside of the vascular tissue. Some vascular bundles have Lechuguilla (Agave lecheguilla Torr.) no fibers at all. Blunden and Binns (16) re- ported trichomes containing up to 11 cells on Lechuguilla is a low-growing agave occurring the leaf margins. The margins of our leaves in the Edwards Plateau and Trans-Pecos contained a vascular bundle with many fibers. Mountains and Basins regions of Texas. Often occurring in extensive colonies, the plant Stem transection blooms once when 3 to 4 years old by producing Not all plants have aboveground stems. The a spikelike panicle at the apex of a stalk stems that do occur are not more than 0.3 m (scape) 1 to 4 m tall. The fruit is a brown or tall. The outside has a nonliving, suberized black capsule. sheath (fig. GE). Underneath is a wide tier of cortical parenchyma that grades into a tier Leaf shape and surface with small, tightly packed parenchyma. Inside Lechuguilla produces 10 to 30 widely radiat- these parenchyma is a tier of about 10 cells ing concave, stiff, grayish- or yellowish-green appearing to be cambial initials (fig. 6F). The leaves 15 to 36 cm long by 2.5 to 3.7 cm wide, main body of the stem is filled with longi- with a broad sheathing leaf base and tapering tudinal vascular bundles made up mostly of to a spine-bearing apex. The margins are white, xylem. Few fibers are present. The vascular bear recurving spines up to 6 mm long and bundles are surrounded by compact, ground spaced about 25 mm apart, and have threadlike parenchyma. Clusters of raphid crystals are extensions. 23 PN-5498 FIGURE 7.—Lechuguilla (Agave lecheguilla Torr.) leaf. A, Upper surface (X 100). B, Lower surface (X 100). C, Upper surface area transection (X 85). D, Inside transection {X 85). 24 Leaf anatomical characteristics have been High Plains and Trans-Pecos Mountains and summarized by Blunden and Jewers (17), Both Basins regions. Growing up to 30 m tall and the upper (fig. 7A) and lower (fig. IB) leaf 24 dm in diameter, it has a somewhat open surfaces are smooth with shallow papillae and crown supported by a massive trunk, and the with no trichomes. Stomata are sunken and root system is extensive but shallow. A bibli- arranged at random rather than in lines. The ography of Populus spp. has been compiled suprastomatal crypts are- covered by 7 to 14 (53) and recently updated (68a), cuticular lips projecting from subsidiary cells. Leaf shape and surface The crypts have two joining air spaces similar to Agave victoria regina as reported by The leaves are 8 to 18 cm long by 10 to 13 cm McClendon (95), wide, simple, alternate, and deciduous; the shape is deltoid to ovate-deltoid, the margin Leaf transection crenate-serrate, the apex acuminate to acute, Both the upper and lower epidermal layers the base truncate to heart shaped, and the sur- have a thick cuticle extending almost to the face lustrous green above and somewhat paler base of the epidermal cells (fig. 7C). The epi- below. Curtis and Lersten (34^) found that the dermal cells are elongated vertically about three marginal teeth exude resin and that unspe- to four times higher than wide. The main body cialized hydathodes and extrafloral nectaries of the leaf contains parenchyma; cells located occur proximal to each glandular tip. near the epidermal layers are smaller (fig. 7C) Both the upper (fig. 8A) and the lower (fig. and more tightly packed than those in the cen- SB) leaf surfaces are smooth with prominent ter (fig. TD), A few raphid and rhombic veins. Rubiaceous stomata occur on both sur- crystals are present in the mesophyll. faces with subsidiary cells (parallel to the long Vascular bundles, enclosed in a sheath of axis of the pore and guard cell). The stomata large cells, are abundant and occur mostly in vary widely in size. The guard cells lie at the arcs parallel to the curvature of the leaf. The surface of the cuticle. A few long, pointed vascular bundles are oriented with the large hairs occurred on the margin ; none were found fiber caps pointing toward the nearest epi- on the veins or lamina. dermis. Blunden and Jewers (17) recognized three types of bundles in lechuguilla. Type A, Leaf transection mainly in central arcs, is composed of primary The structure of the embryonic and develop- and secondary fiber caps at phloem and xylem ing leaf has been described by Smith (139) poles. Type B has a fiber cap covering the and Isebrands and Larson (81). Sun leaves are phloem, but none covering the xylem. Type C thicker than shade leaves (82). In the mature has a bundle of fibers but no vascular tissue. leaf, little cuticle appears on the lamina (fig. In this study (fig. 7, C, D) most of the largest 8C) or midrib (fig. SD) of either leaf surface. vascular bundles are type A, in which the fiber The palisade parenchyma are one (82) or two cap is much more prominent over the phloem cells deep (81). Spongy parenchyma are loosely than over the xylem. Type B is also common. packed and usually are three cells deep. The A few bundles containing only fibers or con- veins are vertically transcurrent. In the midrib taining only vascular tissue also were present. (fig. 8Z)), a layer about three cells deep under The margin comes more or less to a point the epidermis appears to be hypoderm. These and contains numerous fibers with narrow cells are underlain by about three to five lumens as described by Blunden and Jewers parenchyma. The xylem is central, enclosing (17). some pith. The phloem is slightly heart shaped and almost completely encloses the xylem. Salicaceae Stem transection Eastern Cottonv^ood The periderm is light greenish yellow on (Populus deltoides Marsh.) young stems, later becoming gray to almost (Eastern cottonwood is generally distributed black with flattened ridges separated by deep throughout Texas with the exception of the fissures on mature stems. In the mature stem, 25 PN-5499 FIGURE 8.—Eastern cottonwood (Populus deltoides Marsh.}- A, Leaf upper surface ( X 200). B, Leaf lower surface (X 200). C, Leaf lamina transaction (X 266). a rhytidome forms (fig. SE), made up of sev- the outer part of the phellem. The secondary eral phellogens separated by tiers of secondary phloem (fig. 8F) consists of progressive strati- phloem. One layer of phellogen produces numer- fications of fibers and sieve elements plus pa- ous layers of phellem and two or three layers renchyma {25, 93). The fibers are generally of phelloderm. The phellem cells are thin walled one to four cells deep radially and form con- and rectangular to nearly square. A few rec- tinuous tangential bands interrupted only by tangular thick-walled cells were also present as the rays. The sieve tubes are solitary and in reported by Chang (25). Numerous sclereids groups up to five. Phloem parenchyma are scat- were present, occurring both as groups and as tered among sieve elements, forming a sheath more or less tangentially connected layers in around the fiber bands. 26 PN-550Ü FIGURE 8.—Eastern cottonwood (Populus deltoides Marsh.)—Continued. D, Leaf midrib transaction (X 85). E, Trunk periderm transection {X 85). F, Trunk phloem, cambium, and outer xylem transection (X 85). G, Trunk xylem transection (X 77). 27 PN-5501 FIGURE 9.—Black willow {Salix nigra Marsh.). A, Leaf upper surface (X 200). B, Leaf lower surface {X 200). C, Leaf lamina transection (X 200). D, Leaf midrib transection (X 85). The xylem (fig. 8G) is semiring- to diffuse- shape is narrowly lanceolate, the apex acumi- porous and contains moderately small' vessels nate, the margin finely serrate, the base either solitary or in radial multiples of one to rounded, and the surface medium green above five cells. Parenchyma are sparse and generally and paler below. limited to the growth ring boundaries. Fibers The upper {fig. 9A) and lower (fig. 9S) leaf are thin walled and occasionally gelatinous surfaces are both smooth with a few unicellular {86). Rays are uniseriate. hairs. The veins are visible on both surfaces. Stomata occur on both surfaces and are ru- Black Willow (Salix nigra Marsh.) biaceous with usually two subsidiary cells lying outside each guard cell. The subsidiary cells Black willow occurs in all areas of Texas are difficult to delineate in these photos be- except the Trans-Pecos Mountains and Basins cause of the cuticle. The teeth on the margins region. A rapidly growing tree, it attains a have glands. height of 38 m, with a broad, irregular crown and a shallow root system. It is usually found Leaf transection on moist or wet sites {67). A moderately thick cuticle occurs on both Leaf shape and surface epidermises (fig. 9C). In most areas of the lamina, palisade parenchyma are two or three The leaves are 8 to 15 cm long by 6 to 19 mm cells deep under both surfaces with two or three the wide, simple, alternate, and deciduous ; layers of spongy parenchyma in the middle. ■'"Small" means <100 ^um; "lai'ge" means >200 ¡±m Toward the margin, palisade parenchyma {97). sometimes fill the entire lamina under the 28 I ' £ ■■ ' ' ' ^ i— t --• W ¿^ AK ^^B ^B ^V ■Ci*" s m ^s3 PN-5502 FIGURE 9.—Black willow {Salix nigra Marsh.)—Continued. E, Trunk periderm transection (X 77). F, Trunk phloem, cambium, and outer xylem transection (X 77). G, Trunk xylem transection (X 77). epidermises between the veins. The veins are phellem to the outside and two or three layers vertically transcurrent ; the larger ones con- of phelloderm (fig. 957) to the inside. The phel- tain fibers. The midrib (fig. 9D) contains two logens form a rhytidome with secondary phloem superimposed vascular bundles with a tier of tissue, but most of the sieve elements have al- fibers on the outside of each. The xylem is ready collapsed. The phellem and phelloderm either flat or slightly crescent shaped. Phloem cells are flattened. The youngest phellem cells tiers lie between the xylem and fibers. often have thicker tangential walls on the side away from, than on the side toward the Stem transection phellogen (25). The periderm is light brown to black, rough, The secondary phloem (fig. 9F) contains and deeply fissured. The periderm contains alternate tiers of fibers and sieve elements plus phellogens that produce about four layers of parenchyma (25, 93). The fiber tiers are most- 29 PN-5503 FIGURE 10.—Southern waxniyrtle (Myrica cerífera L.). A, Leaf upper surface (X 95). B, Leaf lower surface (X 170). C, Leaf lamina transection (X 235). D, Leaf midrib transection (X 85). \y two or three cells deep and form tangential times two layers. Fibers have thin walls. Rays tiers except where interrupted by the rays. are uniseriate. Sieve tubes are solitary or two or three in short radial multiples. Those near the cambium are Myricaceae rounded; those near the phellog-en are more flattened. Phloem parenchyma occur both as Southern Waxmyrtle tangential lines on either side of the fibers and (Myrica cerífera L.) as a reticulate form among the sieve elements. Southern waxmyrtle is an aromatic species The xylem (fig. 9G) is semiring- to diffuse- that occurs in the Pineywoods, Gulf Prairies porous. Vessels are numerous, moderately small, and Marshes, Post Oak Savannah, and South and thin walled. Those produced in the early Texas Plains of Texas. It usually occurs in wood are larger than those produced in the late sandy swamps or low-acid prairies as a shrub wood. They occur either singly or in radial but may grow to be a tree 12 m tall. multiples of two to seven (usually two or three) (67). Parenchyma are generally limited to the Leaf shape and surface boundaries of the growth ring in one or some- The leaves are 4 to 13 cm long by 6 to 19 30 FIGURE 10.—Southern waxmyrtle (Myrica cerífera L.)—Continued. E, Trunk periderm, phloem, cambium, and outer xylem transection {X 85). F, Trunk xylem transection (X 85). mm wide, simple, alternate, and tardily decidu- upper epidermis is generally composed of small ous; shape is oblanceolate to elliptic, the apex cells with straight walls (fig. IOC), whereas acute or rounded, the margin entire or coarsely the lower epidermal cells are more undulating. serrate above the middle, and the base wedge The palisade parenchyma are usually one or shaped or narrowed. two cells deep. The spongy parenchyma are The surface is dark green. The upper surface loosely packed. Many cells are tanniferous. (fig. lOA) is generally smooth with some long, Veins are vertically transcurrent with large pointed, unicellular hairs and a few yellow and cells around the vascular bundle. Clustered orange-red peltate glands. The long, pointed crystals are abundant in the mesophyll, par- hairs occur primarily on the veins and margin, ticularly adjacent to the veins. The vascular but a few occur on the lamina. The lower sur- bundle of the midrib (fig. 107)) is a crescent face (fig. WB) has many peltate glands and with a tier of fibers both above and below the many ranunculaceous stomata. The peltate bundle. The fibers above the xylem are larger glands produce a characteristic aromatic waxy in diameter than those below the phloem. material. Some of the glands are rounded; Stem transection others, presumably older, are partially col- lapsed. The stomatal pores are mostly covered The periderm is simple with numerous layers by cuticle extensions of the guard cells. of phellem and two to four layers of phelloderm (fig. 10Í7). No rhytidome was found. The phel- Leaf transection lem cells have medium-thick walls and are flat- Peltate glands are supported by partially de- tened tangentially. The phelloderm cells contain pressed, multicelled stalks (fig. 10, C, D). The dark-staining tanniferous materials. The outer 31 PN-5505 FIGURE 11.—Pecan [Carya illinoensis (Wangenh.) K. Koch]. A, Leaf upper surface (X 200). B, Leaf lower sur- face (X 220). C, Leaf lower surface stomata (X 500). D, Leaf lamina transection (X 244). phloem is composed mostly of parenchyma con- Juglandaceae taining dark tanniferous materials and sclereida that are either solitary or in small groups. Pecan Translocating sieve elements are solitary to [Carya ¿lUnoensis (Wangenh.) K. Koch] groups of five among the parenchyma near the Pecan is native to Texas and is found in all cambium. The ends of the rays tend to open areas but the High Plains. It occurs wild, in triangularly toward the outside of the stem. cultivated orchards where it is grown for its The ray parenchyma in the phloem are larger edible fruit, and in populated areas as an orna- than in the xylem. mental. It grows to 45 m tall with a trunk di- The xylem is diffuse-porous with small, al- ameter of 6 to 10.6 dm (65). The crown is most exclusively solitary vessels (fig. lOF). A broad and rounded. It grows mostly on low, few radial multiples, however, do occur. Par- moist, but well-drained soils. enchyma are scattered among the fibers with Leaf shape and surface some in contact with the vessels. A few tend to The leaves are 23 to 50 cm long, alternate, form tangential lines. Fibers have thin walls. deciduous, and odd-pinnately compound. Leaf- Rays vary from one- to four-seriate. lets are 9 to 17, 10 to 20 cm long by 2.5 to 32 PN-5606 FIGURE 11.—Pecan [Carya illinoensis (Wangenh.) K. Koch]^Continued. E, Leaf midrib transection (X 98). F, Trunk periderm and outer phloem transection (X 85). G, Trunk phloem, cambium, and outer xylem transec- tion (X 85). if. Trunk xylem transection (X 85). 33 5 cm, wide, sessile, and curved; the shape is niferous. Some clustered and a few rhombic oblong-lanceolate, the apex acuminate, the mar- crystals are present. gin singly or doubly serrate, and the base In the translocating phloem (fig. IIG), the rounded to wedge shaped and inequilateral. sieve tubes are large and either solitary or in The upper leaflet surface is dark green to multiples up to four cells. Irregular bands of yellowish green and smooth (fig. IIA). The fibers alternate with blocks containing sieve upper epidermis is papillose. A few long, point- elements and phloem parenchyma (8). The ray ed hairs occur on the midrib, veins, and margin. parenchyma contain tanniferous materials. The The lower surface (fig. IIB) has short-stalked, cambium is about five cells deep. peltate glands that secrete resinous material. The xylem (fig. 11, G, H) is ring-porous to The peltate glands are of two sizes. Also, long, semiring-porous (65). Most vessels are solitary, pointed singular and multiple hairs are abun- but a few occur in radial multiples of two to dant, occurring particularly on the veins, most four cells (69). They are round to broadly oval. abundant at the junction of the midrib and The transition from large early wood vessels major veins. Stomata are ranunculaceous. Sto- to small late wood vessels is gradual in wide mata of different sizes occur on the lower rings and abrupt in narrow rings. Late wood surface (fig. IIC). Factors affecting their vessels are small and either solitary or in radial opening, mainly adequate light and soil mois- rows of two or three cells. A moderate amount ture, were studied by Sitton (136). of parenchyma are present as tangential bands, one to four cells deep in the ring and at the Leaf transection margins. Some apotracheal diffuse parenchyma The leaflet lamina has a definite cuticle (fig. occur around the vessels either as solitary cells IID) on the epidermis. Palisade parenchyma or in small aggregates. Fibers are thin to thick are one or two layers deep (120). Spongy par- walled and mostly gelatinous. Rays are one- to enchyma are loosely packed. Large clustered five-seriate. crystals are present in the palisade parenchy- ma, generally occurring near the veins. The Mockemut Hickory veins are vertically transcurrent. A number of {Carya tomentosa Nutt.) parenchyma contain oil droplets. Mockernut hickory occurs in the Pineywoods The midrib (fig. HE) contains a central and Post Oak Savannah areas of Texas, largely superimposed xylem (almost a complete circle) on well-drained uplands. It is a tree that grows separated by pith. Phloem almost entirely en- to 30 m tall with rather short limbs and a closes the xylem. A fiber tier occurs above and broad or oblong crown. Seedling structure has below the vascular tissue. Cells appearing to be been described by Holm (72). hypoderm occur between the epidermis and fibers of the midrib. Leaf shape and surface The leaves are 20 to 60 cm long, alternate, Stem transection deciduous, and odd-pinnately compound. Leaf- The pecan stem has a light brown to grayish lets are seven to nine (rarely five), the lateral brown bark divided into interlacing somewhat ones being sessile ; the shape is oblong to lance- scaly ridges separated by narrow, irregular olate or obovate, the apex acute or acuminate, fissures (65). A rhytidome forms. The phel- the margin serrate, and the base rounded or logens produce both phellem and phelloderm broadly wedge shaped and inequilateral. The upper leaflet surface is dark yellowish (fig. IIF). The phellem may have either thin green and smooth, except for slight papillose or thick walls. The first formed phellem cells structure of the epidermal cells (fig. 12A). are almost square with thin walls when numer- A few peltate glands are scattered on the la- ous rows are produced. About the last 10 rows mina, and a few long, pointed hairs occur on of phellem cells usually have thick walls and the midrib, veins, and margin. The lower sur- are flattened. The phelloderm is usually two face is pale yellowish green and contains tri- to four cells deep. The outer phloem consists chomes and stomata. Many peltate glands are mostly of parenchyma of which many are tan- present, some of which are circular, and others 34 PN-5507 FIGURE 12.—Mockernut hickory [Carya tomentosa (Poir.) Nutt.]. A, Leaflet upper surface (X 100). B, Leaflet lower surface (X 100). C, Leaflet lamina transection (X 378). D, Leaflet midrib transection (X 77). are four-pointed (fig. 12B). Peltate glands oc- Jackson (82) reports sun leaves with two rows. cur on the lamina, midrib, and large veins. The spongy parenchyma are loosely packed Solitary or tufted hairs with unicellular com- (72), Veins are vertically transcurrent with a ponents are present on the veins (fig. 12, B, C). sheath of large, usually thick-walled cells. The The densest concentration of hairs occurs at larger veins contain fibers. Large clustered the junction of the large veins with the midrib. crystals occur in the palisade parenchyma lay- Stomata vary in size and are ranunculaceous ; er, and small ones occur in the spongy pa- they occur only on the lower surface. renchyma. Some rhombic crystals were also present in the veins. Leaf transection The midrib (fig. 12D) of the leaflet has small There is a thin cuticle on epidermal cells of epidermal cells above two layers of hypoderm. both surfaces (fig. 12C). The palisade paren- Inside on the lower side are water storage cells chyma are usually one cell thick; however, and parenchyma. A central superimposed cylin- 35 Wrí¥ r^M PN-5508 FIGURE 12.—Mockernut hickory [Cari/a tomentosa (Poir.) Nutt.]—Continued. E, Trunk periderm transection (X 85). F, Trunk phloem, cambium, and outer xylem transection {X 85). G, Trunk xylem transection ( X 85). 36 der of xylem is separated by parenchyma. The Leaf shape and surface phloem encircles the xylem and appears more The leaves are 30 to 60 cm long, pinnately or less in bundles separated by lignified strands compound, alternate, and deciduous. Leaflets of cells connecting the xylem with the outer are 11 to 23, 8 to 13 cm long by 2.5 to 5 cm fibers. The entire vascular bundle is encircled wide, and sessile or short stalked; the shape by three or more layers of fibers. is ovate-lanceolate, the apex acute to acuminate, Stem transection the margin finely serrate, and the base in- equilateral and rounded or subcordate. Morphology of the cotyledonary node has The upper leaflet surface is lustrous dark been described by Conde and Stone (29). In yellowish green. The upper epidermal cells are the tree, the outer bark is gray, close, with low, papillose with a few capitate glands (fig. 13A). rounded interlacing ridges and shallow fissures. The veins are conspicuous. Also (not shown), A rhytidome forms with phellogens producing numerous long, pointed hairs that are either both phellem and phelloderm between tiers of solitary or in triplets occur on the midrib, large secondary phloem comprised mostly of paren- veins, and occasionally on the lamina. chyma (fig. 12E). The phellem is about 10 The lower leaflet surface is covered with cells deep, and the phelloderm is about 2 or 3 large numbers of long, pointed hairs and a few cells deep. Numerous clustered and some rhom- capitate glands associated with the veins (fig. bic crystals are common among the phloem 13-ß). A few yellow peltate glands also occur parenchyma but not in the rays (70). The on the veins (22). Stomata occur only on the translocating phloem (fig. 12F) contains large sieve tubes that are either solitary or in groups of up to four cells. Numerous thin-walled fi- bers are present either as tangential lines one to three cells deep or as groups. Phloem paren- chyma generally form tangential lines and are tanniferous. The xylem (fig. 12G) is ring-porous. Both the large early wood and small late wood ves- sels are largely solitary, but some do occur in multiples up to four cells. Vessels grade im- mediately from large ones in the early wood to small ones in the late wood. Most parenchy- ma are apotracheal, either as scattered individ- ual cells or in continuous bands one or two cells wide both in the ring and at the margin. A few, however, are paratracheal. Fibers are mostly thick walled, with most being gelatinous. Rays are one- to four-seriate. Black Walnut (Juglans nigra L.) Black walnut occurs in all areas with the ex- ception of the South Texas Plains, High Plains, and Trans-Pecos Mountains and Basins regions of Texas. It grows to 38 m tall with a rounded crown and occurs mostly on fertile, moist soils. Bibliographies of ecological and silvicultural information on black walnut have been made by Funk (56) and Billow and Hawker (UO) ; PN-5509 FIGURE 13.—Black walnut (Juglans nigra L.), A, Leaf- seedling structure has been described by Holm let upper surface ( X 200). B, Leaflet lower surface (72) and Davey (36). (X 200). 37 PN-5510 FIGURE 13.—Black walnut {Juglans nigra L.)—Continued. C, Leaflet lamina transection (X 218). D, Leaflet mid- rib transection (X 86). E, Trunk periderm and outer phloem transection (X 85). F, Trunk phloem, cam- bium, and outer xylem transection (X 85). G, Trunk xylem transection (X 93). 38 lower surface and are ranunculaceous among Leaf shape and surface the papillose epidermal cells. The leaves are 4 to 9 cm long by 2.5 to 5 Leaflet transection cm wide, simple, alternate, and deciduous; the shape is rhombic-ovate, the apex acute, the A prominent cuticle occurs on the epidermal margin doubly serrate or some lobed with dou- cells of both surfaces (fig. 13C). The palisade ble serrations, and the base cunéate. parenchyma are mostly two cells high. Both The upper surface is dark green with an un- palisade and spongy parenchyma are tightly dulating contour (fig. 14A). Veins are con- packed. The veins are vertically transcurrent. spicuous. A few long, curling, pointed and a Large clustered crystals occur in the palisade few short, pointed hairs occur on the upper parenchyma ; small clustered crystals are pres- surface. ent in the parenchyma of the midrib. The lower surface is medium green. Epider- The midrib transection (fig. 13D) has a ver- mal cells on the lower surface are papillose tical ridge of parenchyma, many of which con- with ranunculaceous stomata (fig. 14ß). Guard tain crystals. A closed, superimposed xylem cells of the stomata are convex shaped. Large, separated by parenchyma occurs in the center short-stalked, circular glandular scales and and is almost completely surrounded by suc- long, pointed hairs are present on the lower cessive tiers of phloem and fibers. Several surface. Stalks of the glandular scales are epidermal cells have projecting segments of multicelled. Often many hairs are present and unicellular hairs. may be either white or reddish brown. Stem transection Leaf transection The outer bark is brown to grayish black, Only a thin cuticle occurs on both epidermises divided by deep, narrow fissures. A rhytidome (fig. 14(7). Most upper epidermal cells have forms with phellogens producing phellem, and dark-staining mucilage, whereas only a few of phelloderm that cut off tiers of secondary the lower epidermal cells contain mucilage. phloem now consisting mostly of parenchyma Palisade parenchyma are about three cells deep. and fibers (fig. ISE) and occasional clusters Spongy parenchyma are loosely packed. The of sclereids. The translocating phloem region veins are vertically transcurrent with hypo- (fig. ISF) consists of large sieve tubes with dermlike cells connecting the vascular bundles companion cells, smaller parenchyma, and short with the upper and lower epidermal cells. Small intermittent bands of fibers. Parenchyma fre- clustered crystals are present near the veins in quently contain a dark staining substance (93), the spongy parenchyma. The xylem is ring-porous (fig. 13G). Most The midrib (fig. 14D) has a concave xylem. early wood vessels are large and solitary, but The phloem forms a crescent-shaped tier below some are grouped into as many as three. Ves- the xylem,. Outside the phloem is a tier of fi- sels quickly grade from large to small from the bers. Some large cells among the phloem and early wood to the late wood. Parenchyma are fibers contain tanninlike material. Some clus- apotracheal-diffuse to banded and scanty para- tered crystals are present in the parenchyma tracheal to vasicentric. Lines of banded paren- between the fiber tier and the epidermis. chyma are mostly one cell wide. Fiber tracheids are thin to moderately thick walled. Rays are Stem transection one- to five-seriate. The outer bark of river birch has the un- usual characteristics of being thin, reddish Corylaceae brown to grayish, and peeling into conspicu- River Birch (Betula nigra L.) ously curled, papery strips. This species de- velops a rhytidome (fig. 14£') with conspicuous River birch is the only birch found in Texas phellogens producing phellem and phelloderm and occurs in the river bottoms of the Piney- cells that separate remnants of secondary woods and Post Oak Savannah. It grows to phloem consisting mostly of parenchyma and 27 m high. large groups of sclereids. Phellem cells are 39 PN-5B11 FIGURE 14.—River birch (Betula nigra L.). A, Leaf upper surface (X 150). B, Leaf lower surface (X 200). C, Leaf lamina transection (X 395). Z), Leaf midrib transection (X 85). rectangular; the phelloderm cells are more are mostly three and four cells wide containing rounded. Nontranslocating phloem consists of tanniferous parenchyma cells. No phloem fibers parenchyma, frequent large groups of sclereids, are present. Chang (25) indicates that the bark and more or less flattened sieve elements. In of river birch is more similar to sweet birch the translocating phloem (fig. 14F), usually (Betula lenta L.) and yellow birch (Betula two or six sieve tubes occur between the rays alleghaniensis Britten) than to European white in tiers three to eight cells deep. The sieve tubes birch (Betula alba L.), water birch (Betula are polygonal in shape, tending to be oval and occidentalis Hook), gray birch (Betula populi- elongated tangentially. Parenchyma occur both folia Marsh.), or paper birch (Betula papyri- among the sieve elements and in tangential fera Marsh.). tiers two or three cells deep. Often the paren- The xylem is diffuse-porous with the early chyma contain tanniferous substances. Rays wood vessels being slightly larger than the late 40 PN-B512 FIGURE 14.—River birch {Betula nigra L.)—Continued. E, Trunk periderm transection (X 85). F, Trunk phloem, cambium, and outer xylem transection ( X 85). G, Trunk xylem transection ( X 85). wood vessels (fig. 14G). Vessels occur singly, are often flattened radially. Parenchyma are in short radial files, or in small groups of scanty, being apotracheal as cells diffuse among usually two to five cells. Vessel members have the fiber tracheids, paratracheal along the ves- perforation plates containing a maximum of 10 sels, and terminal forming ring boundaries to 18 bars, which is fewer than most other (60). Fiber tracheids are thin to moderately Betula species (HS). Vessels in the late wood thick walled. Rays are one- to five-seriate. 41 PN-5513 FIGURE 15.—American hornbeam (Carpinus caroliniana Walt.). A, Leaf upper surface (X 200). B, Leaf lower surface ( X 200). C, Leaf lamina transection ( X 435). American Hornbeam the apex acute or acuminate, the margin doubly (Carpinus caroliniana Walt.) serrate, and the base rounded, wedge shaped, or heart shaped, often inequilateral. American hornbeam occurs in the Piney- The upper leaf surface is dull dark green woods, Gulf Prairies and Marshes, and Post with a papillose surface (fig. ISA). A few long, Oak Savannah of Texas. A small bushy tree, pointed hairs are present on the midrib and rarely attaining a height of 11 m, the species large veins. None were found on the lamina. generally grows as an understory in mixed The lower surface is lighter green than the hardwoods in shaded areas on moist soils. upper surface and has a papillose surface with Leaf shape and surface prominent veins (fig. 15B). Long, pointed hairs are present on the midrib and large veins. Most The leaves are 5 to 10 cm long by 2.5 to 5 are present at the junctions of the midrib and cm wide, simple, alternate, deciduous, and large veins. Ranunculaceous stomata are pres- sometimes curved; the shape is ovate to oval, ent only on the lower surface. 42 PN-5514 FIGURE 15.—American hornbeam {Carpinus caroUniana Walt.)—Continued. D, Leaf midrib transection (X 110). E, Trunk periderm and outer phloem transection (X 85). F, Trunk phloem, cambium, and outer xylem (X 85). G, Trunk xylem transection (X 85). 43 Leaf transection ondary phloem (fig. 15F) consists of numer- The epidermal cells on the upper surface are ous small groups of sclereids among the par- sHghtly larger than those on the lower surface enchyma. The translocating sieve tubes are (fig-. 15C). In most cases, the palisade paren- large and form a tier four cells deep. Some chyma are only one cell deep, and the spongy parenchyma lie among the sieve elements. The parenchyma are loosely packed. Veins are ver- raylike tissue in the center is the edge of a tically transcurrent. Large solitary rhombic bud trace. crystals occur in the palisade region. The xylem, is diffuse-porous (fig. 15G). Ves- The leaf midrib (fig. 15D) has a super- sels are small, mostly angular, and arranged imposed, central xylem separated by fibers and in radial files of two to six cells. However, phloem. The lower part of the xylem is much some are solitary, and a few occur in small larger than the upper part. Phloem occurs al- clusters. The vessel walls are thin (60). Paren- most entirely around the lower xylem and at chyma are apotracheal and marginal. Apotra- the bottom of the upper part. Thick-walled cheal parenchyma are abundant as single-cell fibers encircle and separate both vascular tangential bands between the rays and sparse bundles. as marginal and diffuse cells. Fiber tracheids are thin to moderately thick walled. Rays are Stem transection mostly one- to three-seriate, with a few to five .The outer surface of the bark is character- cells wide. The one-cell-wide rays are homo- istically smooth, blue gray, sometimes mottled cellular. The wide aggregate rays may either with light or dark patches, and fluted into consist of units similar to the narrow homo- musclelike separations. The periderm is com- cellular rays or may include fibers and vessels. prised of tiers of rectangular phellem and The ray cells may contain crystals {Í43). phelloderm on the outside and inside of the phellogen, respectively (fig. 15E). The phello- Eastern Hophornbeam derm cells are larger than the phellem cells. [Ostrya virginiana (Mill.) K. Koch] Underneath is an almost continuous tier of large sclereids about four deep; some rhombic Eastern hophornbeam occurs in the Piney- crystals lie among the sclereids. The outer sec- woods. Gulf Prairies and Marshes, and Cross PN-5515 FIGURE 16.^Eastern hophornbeam [Ostrya virginiana (Mill.) K. Koch]. A, Leaf upper surface (X 200). B, Leaf lower surf ace (X 240). 44 Timbers and Prairies of Texas. It usually grows 6 to 12 m tall but may grow to 18 m with a trunk diameter of 9 dm. The crown is rounded and slender. This tree usually grows as an understory species in mixed hardwoods largely on moist sites. Leaf shape and surface The leaf is 6 to 11 cm long by 4 to 6 cm wide, alternate, simple, and deciduous ; the shape is ovate to oblong-lanceolate, the apex acute or acuminate, the margin sharply doubly serrate, and the base rounded, heart shaped, or wedge shaped, often inequilateral. The upper epidermal surface is smooth (fig. 16A). A few long, pointed hairs occur on the lamina, and many occur on the midrib and large veins. The lower leaf surface is lighter green than the upper surface. Many long and short hairs are present (fig. 16ß). Also, a club-shaped glandular hair consisting of a short stalk and an ellipsoidally shaped head occurs at the top of the photo (fig. 16B}. Ranuncu- laceous stomata occur only on the lower sur- face. Guard cells are slightly raised above the level of the surrounding ground epidermal cells. Extension of the cuticle from the guard cells partially covers most pores. Leaf transection The leaf has little cuticle (fig. 16C). Pali- sade parenchyma are one cell deep, and spongy parenchyma are loosely packed. A stoma on the lower epidermis shows the cuticle extension of the guard cell over the pore. The medium-sized veins are vertically transcurrent. Large solitary rhombic crystals occur in the palisade region. In the midrib (fig. 16/)), the xylem is more PN-B516 or less keyhole shaped with the phloem at the FIGURE 16.—Eastern hophombeam [Ostrya virginiana (Mill.) K. Koch]-—Continued. C, Leaf lamina sides and bottom. Parenchyma occur at the transection (X 500). D, Leaf midrib transection center. Fibers surround the vascular tissue. (X 160). Small clustered crystals occur in some paren- chyma cells. of sclereids two or three cells deep. The phloem is stratified into alternate tiers of sieve ele- Stem transection ments plus parenchyma and discontinuous tiers The outer bark is thin, grayish brown, and of fibers (fig. \QE). broken into small, narrow, oblong plates that The hard, strong xylem is diffuse-porous, give it a characteristically shreddy appearance. with the early wood vessels slightly larger than The periderm consists of a thick tier of large, the late wood vessels (fig. 16, E, F). Vessels thin-walled phellem cells (fig. 16E). The phel- are small and occur either singly or in radial logen produces several layers of phelloderm. files of two to seven cells {60). The vessels at Underneath the phelloderm is a continuous tier the outermost end of the file often become pro- 45 PN-5517 FIGURE 16.—Eastern hophornbeam {Ostrya virginiana (Mill.) K. Koch]—Continued. E, Trunk periderm, phloem, cambium, and outer xylem transection (X 85). F, Trunk xylem transection (X 85). gressively smaller. Parenchyma are apotracheal wide, thin and firm, alternate, simple, and de- and marginal. The apotracheal parenchyma ciduous; the shape is oblong-obovate, the apex form one-cell-wide bands between the rays. rounded, and the margin with 7 to 11 oblique, Marginal parenchyma along the ring bounda- elongate, and rounded lobes. The terminal lobe ries are sparse. Fiber tracheids are medium in usually is shallowly three-parted. White oak, thickness. Rays are one- to three-seriate. which belongs to the Leueobalanus subgenera, has no spinose teeth. The leaf base is wedge Fagaceae shaped. The upper surface is bright green and is White Oak (Quercus alba L.) free from trichomes (fig. 17A). The epidermal White oak grows in the Pineywoods, the Gulf cells are slightly papillose, and the veins are Prairies and Marshes, and the Post Oak Savan- prominent. nah areas of Texas. It can grow to 45 m tall The lower surface is lighter green than the with a broad open crown. White oak can grow upper surface and usually is glaucous. Sparse on gravelly ridges and rich uplands, but makes numbers of small, elongated hairs were present its best growth on bottom lands. Juvenile varia- on a leaf collected in May (fig. 17B). A leaf tion in the growth of five members of the white collected in the fall had some solitary, long, oak group (Leueobalanus), including Quercus pointed hairs and tufted, long, pointed hairs at alba L., has been described by Santamour and the base of the midrib and large veins. A few Schreiner (128). tufts of hairs arose on the lamina. The lower epidermal cells were papillose with a waxy lay- Leaf shape and surface er. Stomata were ranunculaceous and were Leaves are 13 to 23 cm long by 5 to 10 cm present only on the lower surface. Figure 17C 46 PN-5518 FIGURE 17.—White oak (Quercus alba L.). A, Leaf upper surface (X 100). B, Leaf lower surface (X 100). C, Leaf lower surface stomata ( X 525). D, Leaf lamina transection ( X 390). shows the stomata on a leaf collected in the and small clustered crystals are present in the fall; a cuticle extension on the guard cells par- spongy parenchyma. tially covers most pores. Also, the wax is not The midrib (fig. 17E) has a more or less as prominent as on the leaf collected in the cylindrical xylem with a horizontal tier in the spring (fig. ITS). middle. Phloem occurs almost entirely around the xylem cylinder underneath the middle tier Leaf transection of xylem. A fiber tier entirely encircles the The leaf has a cuticle on both epidermal sur- vascular bundle. faces (fig. 17Z>). The upper epidermal cells are mucilaginous and are slightly larger than the Stem transection lower epidermal cells. Palisade parenchyma are The anatomies of the seedling stem and buds one cell thick, and the spongy parenchyma are have been described by Langdon (92) and loosely packed. Medium-sized veins are verti- Mogensen {lO-k-), respectively. On the mature cally transcurrent. Larger veins have fibers. plant, the outer bark is light ashy gray and Rhombic crystals are present in some veins, irregularly plated with narrow, rounded ridges. 47 IM PIO Äs 3 OP I¡^~¿Á 9 l^s^Ä J1 H^ JB SHM1 ^ H PN-5519 FIGURE 17.—White oak {Quercus alba L.)—Continued. E, Leaf midrib transection (X 77). F, Trunk periderm and outer phloem transection (X 77). G, Trunk phloem, cambium, and outer xylem transection {X 77). H, Trunk xylem transection (X 77). In large trees, the bark grows up to 5 cm thick sclereids. Many groups have rhombic crystals. with the rhytidome and living secondary Parenchyma often contain tannin (25). Some phloem usually each about 2.5 cm thick (25). fibers are present in discontinuous tangential The rhytidome is comprised of several phello- bands two or three cells wide. gens that cut off tangential tiers of secondary The translocating phloem (fig. 17G) is a phloem (fig. 17F). Phellogens produce both continuous tier of large sieve tubes and com- phellem and phelloderm. The phellem is usually panion cells separated tangentially by tiers of comprised of several two- to eight-cell tiers fibers and radially by rays. The sieve tubes of thin-walled cells separated by one or two are slightly polygonal and tend to be oval in (occasionally as many as six) layers of thick- shape. Apparently all but the last three or four walled cells. Phellem cells are flattened. Phel- rows of sieve elements produced during the loderm is usually one or two cells deep. growing season die the same year they are The outer living phloem is composed mostly produced (6). of parenchyma and numerous groups of large Chang (25) lists the bark diagnostic features 48 of the white oak group, Leucobalanus (or Lepi- wet and dry sites but is generally found on the dohalanus), including Quercus alba L., as hav- drier upland soils (160). ing (1) a rhytidome usually soft, rather loose, Leaf shape and surface and often wider than the living secondary phloem, (2) periderm layers conspicuously The leaf is 13 to 25 cm long by 10 to 13 cm alined in tangential lines, but broken regularly wide, alternate, simple, and deciduous; the along the radius by phloem rays, (3) broad shape is ovate to obovate, the apex acuminate, phloem rays usually extending straight through and the margin three to seven bristle-tipped the living secondary phloem into the rhytidome lobes (often with shallowly three-lobed and without dilating, and (4) fibers and sclereids deeply five- to seven-lobed leaves on the same that tend to be alined in discontinuous tangen- tree). Bristle-tipped lobes are characteristics tial lines. of members of the Erythrobalanus subgenera In oak xylem, there is also much interest in (red oak group). The leaves are often curved. correlating the common features among the The base is rounded to broadly wedge shaped. The upper surface is dark green and smooth Leucobalanus (white oak group) and Erythro- (fig. ISA). Although not shown in figure ISA, balanus (red oak group) (108, 159, 17U, 175, 176). Panshin and de Zeeuw (108) suggest a few stellate hairs occur on the lamina; more occur on the base of the midrib and margin. that the characteristics of the white oak group The epidermal cell shapes are visible. The low- are (1) a heartwood that is light to dark brown er surface is paler green than the upper surface without flesh color, (2) a generally abrupt and has many brown to grayish white stellate transition from early to late wood, (3) late wood pores that are thin walled and more or less angular, and (4) large rays averaging 13 to 32 mm tall, with some exceeding 38 mm tall. The xylem is markedly ring-porous. Early wood vessels are large and rounded (fig. 17H). Although not shown, some early wood vessels had tyloses 3 to 5 ^im thick (31, 101, 175). Vessels grade abruptly from large in early wood (fig. 17H) to small in late wood (fig. VIG). Late wood vessels are angled to oval, have thin walls, and are more or less grouped. Both paratracheal and apotracheal parenchyma are abundant. The parenchyma (1) join the early wood vessels with the rays, (2) compose most of the cells joining the small late wood vessel together, and (3) form more or less reg- ular one-cell tangential lines in the outer por- tion of the growth ring. Fibers are medium thick to thick walled and frequently gelatinous. Rays are of two types: (1) 1- or 2-seriate and (2) 12- to 30-seriate (not shown). Southern Red Oak (Quercus falcata var. falcata Michx.) Southern red oak occurs in the Pineywoods, Gulf Prairies and Marshes, and Post Oak Sa- vannah areas of Texas. It attains a height of PN-5520 FIGURE 18.—Southern red oak (Quercus falcata var. 25 m with a trunk 6 to 9 dm in diameter. The falcata Michx.). A, Leaf upper surface (X 165). crown is large and rounded. It grows both on B, Leaf lower surface (X 215). 49 PN-5521 FIGURE 18.—Southern red oak (Quercus falcata var. falcata Michx.)—Continued. C, Leaf lower surface stomata (X 1,300). D, Leaf lamina transection (X 360). E, Leaf midrib transection (X 87). F, Trunk periderm and outer phloem transection (X 85). trichomes (fig. 18ß). The trichomes are numer- cura on both epidermal surfaces. Upper epi- ous and almost completely mask the epidermis. dermal cells are mucilaginous and are larger Ranunculaceous stomata occur only on the low- than the lower epidermal cells. Palisade paren- er surface (fig. 18C). The cuticle of the guard chyma are one to two cells deep; the spongy cell rises above the level of the ground epider- parenchyma are loosely packed. Veins are ver- mal cells. Edges of the guard cells are wrinkled tically transcurrent. Some fibers and solitary rather than being straight where they join (fig. rhombic crystals are present in the larger veins. 18C). Stellate hairs are present on the lower surface. Large clustered crystals are present among the Leaf transection palisade parenchyma, and small clustered crys- In the lamina (fig. 18D), a thin cuticle oc- tals are present among the spongy parenchyma. 50 - A'.. :^:fe -'ö. ^«-::,.„ PN-5522 FIGURE 18.—^Southern red oak {Quercus fálcala var. falcata Michx.)—Continued. G, Trunk phloem, cambium, and outer xylem transection (X 71). H, Trunk xylem transection (X 71). The midrib (fig. ISE) has a more or less spaced, forming curved scales or tangentially oval xylem with a horizontal tier in the middle. extended and not much broken by the phloem Phloem almost completely encircles the xylem rays; (3) broad phloem rays often become di- and lies inside under the horizontal middle tier lated early in the inner living phloem and of xylem. Fibers ring the outside of the phloem. spread widely at their terminal regions; and (4) fibers and sclereids in the secondary Stem transection phloem often tend to be loosely arranged. Of The outer bark is thick, nearly grayish black these four items, (2) and (4) seemed to be true with deep furrows and broad scaly ridges. The of this sample. inner bark is slightly yellow. The outer protec- There is much interest in correlating the tive covering is a rhytidome where the phello- common features between the Leucahalanus gen produces numerous layers of phellem in {white oak group) and Erytkrobalanus (red the remnants of secondary phloem (fig. 18F). oak group) that includes southern red oak {108, Residual nontranslocating phloem consists of 159, 174, 175, 176). Panshin and de Zeeuw dark-staining parenchyma and clusters of fi- {108) suggest that the characteristics of the bers and sclereids. The inner phloem has a con- red oak group are: (1) the heartwood is pink- tinuous thin tier of translocating sieve elements ish or pale reddish brown, (2) the transition about four cells deep next to the cambium (fig. from early to late wood is gradual to more or 18G). Outside the translocating sieve elements less abrupt, (3) early wood vessels in the heart- are stratified tiers of parenchyma and fibers wood are usually open, (4) late wood vessels plus sclereids. Rays do not extend deep into the are thick walled and rounded, and (5) large phloem. rays average 6 to 13 mm tall, rarely taller than ■Chang (25) indicates bark characteristics of 38 mm. the Erytkrobalanus as: (1) the rhytidome is The xylem is ring-porous (fig. 18, G, H). usually hard, firm, and about the same or nar- Early wood vessels are large and usually two rower than the inner living secondary phloem ; cells deep. The transition is abrupt to small late (2) periderm layers are often irregularly wood vessels. Late wood vessels are solitary, 51 PN-5523 FIGURE 19.—Blackjack oak {Quercus marilandica Muenchh.). A, Leaf upper surface {X 130). B, Leaf lower sur- face (X 130). C, Leaf lamina transection (X 202). rounded, and thick walled. Both paratracheal balanus subgenus, occurs in the Pineywoods, and apotracheal parenchyma are abundant. The Gulf Prairies and Marshes, Post Oak Savannah, paratracheal parenchyma occur around both the Edwards Plateau, and Rolling Plains of Texas. early and late wood vessels. The apotracheal It attains a height of 18 m and a trunk diam- parenchyma are often diffuse toward the outer eter of 6 dm. The crown is usually rounded. It margins of large rings and in one-cell bands grows largely on upland, dry, clayey soils with between the rays. Fibers are medium thick to other hardwoods. thick walled and frequently gelatinous. Rays are of two kinds: (1) the numerous narrow Leaf shape and surface type, 1- to 2-seriate, and (2) the broad type, The leaves are 8 to 18 cm long by 5 to 13 cm 12- to 30-seriate. wide, alternate, simple, deciduous, stiff, leath- Blackjack Oak ery, and obovate; the apex is obtuse, the mar- gin more or less three-lobed to entire with (Quercus marilandica Muenchh.) bristle tips, and the base rounded, cordate, or Blackjack oak, a member of the Erytkro- wedge shaped. 52 Ml ::■•■ i*i''^-^,ï Warn '■*■ : ■ Tl^ PN-5524 FIGURE 19.—Blackjack oak {Quercus marilandica Muenchh.)—Continued. D, Leaf midrib transection (X 85). E, Trunk periderm and outer phloem (X 85). F, Trunk phloem, cambium, and outer xylem (X 85). G, Trunk xylem transection {X 85). 58 The upper surface is dark green and lustrous. divided into rough, square blocklike plates. It The upper epidermal surface is slightly papil- is a rhytidome made up of phellogens that pro- lose with prominent veins (fig. 19A). A vari- duce phellem on the outside and phelloderm. to ety of appendages are present, including a the inside (fig. 19E). The remnants of second- medium concentration of stellate hairs and pel- ary phloem cut off by the phellogens contain tate glands of various sizes. mostly dark-staining parenchyma and clusters The lower leaf surface is light green with of large sclereids. Phellogens are mostly inter- many elongated, tufted hairs {fig. 19-B). These connecting, forming curved scales. The rays hairs give the leaf a scurfy, pubescent feel. broaden progressively from the cambial region Ranunculaceous stomata occur only on the low- outward with the parenchyma transforming to er surface. The cuticle extension on the guard sclereids. The translocating phloem (fig. 19F) cells covers part of the pore. is composed of large sieve tubes and companion Leaf transaction cells. Sieve tubes form a tier up to 12 cells deep. Parenchyma are interspersed among the sieve The leaf lamina (fig. 19C) has a prominent elements and also sometimes form one-cell tan- cuticle on both surfaces. Upper epidermal cells gential lines of tanniferous cells in the sieve are mucilaginous and are larger than the lower element area. Groups of fibers and sclereids epidermal cells. Palisade parenchyma are about with rhombic crystals are numerous outside three cells deep. The spongy parenchyma are the translocating area in the living secondary rather tightly packed and lie in vertical rows. phloem. Veins are vertically transcurrent, and many contain fibers and rhombic crystals. The xylem is ring-porous (fig. 19, F, G). The The midrib (fig. 19D) has a more or less large early wood vessels are round and mostly oval-shaped xylem with a horizontal tier in the two cells deep. Vessels on the inner rings con- middle. Phloem occurs almost entirely around tain tyloses. Transition from early to late wood the xylem cylinder and below the horizontal tier is abrupt. The small, late wood vessels are of xylem. A fiber tier entirely encircles the round to slightly ovate and have thick walls. vascular bundle. Both paratracheal and apotracheal parenchyma are abundant. Paratracheal parenchyma occur Stem transection around both the large and small vessels. The The outer bark is thick, brown or black, and apotracheal parenchyma occur in one-cell-wide PN-5525 FIGURE 20.—Water oak (Quercus nigra L.). A, Leaf upper surface (X 100). B, Leaf lower surface (X 90). 54 tangential lines, particularly in the late wood. surface. The cuticle on the guard cells partially Rays include both the narrow type, 1- and 2- covers the pore. seriate wide, and the broad type, 10- to 30- seriate. Leaf tran section The leaf lamina (fig. 20/)) has a cuticle on Water Oak (Quercus nigra L.) both epidermal surfaces. Upper epidermal cells are mucilaginous and are larger than lower Water oak occurs in the Pineywoods, Gulf epidermal cells. Palisade parenchyma are one Prairies and Marshes, and Post Oak Savannah or two cells deep, and spongy parenchyma are of Texas. It attains a height of 25 m with a loosely packed with some small clustered crys- round crown and a trunk 6 to 9 dm in diam- tals. The veins are vertically transcurrent with eter. Best development is made on the better some containing fibers and rhombic crystals. drained loamy or clay ridges in the bottom; The midrib (fig. 20^) has a more or less however, it can grow on upland clay soils {67). oval-shaped xylem with a horizontal tier in the Leaf shape and surface middle that is almost joined with the top tier. Phloem lies almost entirely around the xylem Leaves are 5 to 10 cm long and 2.5 to 5 cm and underneath the middle tier. A tier of fibers wide, alternate, simple, and persistent. The surrounds the vascular bundle. Some cells out- shape is variable, being spatulate, obovate, ob- side the fibers contain rhombic crystals and long or long and narrow; the apex is acute to occasionally clustered crystals. obtuse, the margin entire, three-lobed at apex, or variously pinnatified-lobed, and the base Stem transection mostly acute to wedge shaped. Outer bark is gray black with irregular The upper surface is lustrous green and is patches of rough, wide, scaly ridges. It is a rather smooth with the epidermal cells giving rhytidome with the phellogens producing a wide a slight papillose appearance (fig. 20A). Veins tier of phellem on the outside and usually two are prominent. A sparse number of collapsed layers of phelloderm on the inside (fig. 20F). glandular hairs are present. The lower surface Phellogens usually form in tangential lines of the leaf has a dense concentration of glandu- rather than in arcs. In the phellem, about six lar hairs, a sparse number of long, pointed cell layers of thin-walled cells often are sepa- hairs, and some stellate hairs (fig. 20, B, C). rated by one or two layers of thick-walled cells. Glandular hairs appear to disintegrate later in The outer living secondary phloem contains the year, leaving only the base. Stomata are dark-staining parenchyma, groups of large ranunculaceous and occur only on the lower sclereids with rhombic crystals, and more or PN-5B26 FIGURE 20.—Water oak (Quercus nigra L.)—Continued. C, Leaf lower surface trichomes (X 200). D, Leaf lamina transection (X 330). 55 PN-5527 FIGURE 20.—Water oak {Quercus nigra L.)^Continued. E, Leaf midrib transection (X 85). F, Trunk periderm transection (X 85). G, Trunk phloem, cambium, and outer xylem (X 85). iî, Trunk xylem transection (X 85). 56 less continuous tangential bands of fibers two mostly 1- to 3-seriate; and (2) broad, 10- to or three cells deep. Most phloem rays extend 30-seriate. from the cambium outward through the phello- gens and remain about the same width. Toward Willow Oak (Quercus phellos L.) the outside, many ray parenchyma differen- Willow oak occurs in the Pineywoods, Gulf tiate into sclereids. The translocating phloem Prairies and Marshes, and Post Oak Savannah is a continuous tier, except for the rays, outside areas of Texas. It grows to a tree 30 m tall with the cambium (fig. 20G). The translocating a trunk 12 dm in diameter. The crown is oval, phloem is 6 to 15 sieve tube cells wide. rounded, or broad-oblong. Willow oak grows The xylem is ring-porous {fig. 20H) {67). usually in bottom land with poorly drained loam Early wood vessels are large and usually two or clay flats (66). However, it is used often as or three cells wide. Many contain tyloses. The an ornamental on upland sites in the South. large, early wood vessels grade abruptly to small, round to ovate, thick-walled late wood Leaf shape and surface vessels. Abundant parenchyma are both para- The leaves are 5 to 13 cm long by 8 to 25 tracheal and apotracheal. Paratracheal paren- mm wide, alternate, simple, and deciduous ; the chyma lie adjacent to both the early and late shape is linear to linear-lanceolate, the apex wood vessels. Apotracheal parenchyma are both acute with a bristle tip, the margin entire, and diffuse as scattered small clusters among the the base cunéate. fibers and as tangential lines mostly one cell The upper surface is bright green with a thick. Fibers are thick walled and sometimes slightly papillose texture and prominent veins gelatinous. Rays are of two kinds: (1) narrow, (fig. 21A). It has no trichomes. The lower sur- PN'5528 FIGURE 21.—Willow oak (Quercus phellos L.). A, Leaf upper surface (X 200). B, Leaf lower surface (X 200). C, Leaf lamina transection (X 338). 57 face is lighter green than the upper surface. A cells are mucilaginous and are larger than the few stellate hairs arise at the junction of the lower epidermal cells. Palisade parenchyma are midrib and main veins. Ranunculaceous sto- one cell deep; spongy parenchyma are loosely mata occur only on the lower surface (fig. packed and occasionally contain small clustered 21B). The extension of the guard cells partially crystals. The veins are vertically transcurrent covers the pore. The lower surface may vary and often contain fibers and rhombic crystals. from smooth to slightly pubescent. The midrib (fig. 21D) has a more or less oval xylem. Phloem almost completely encircles Leaf transection the xylem, and a tier of phloem lies horizontally The lamina (fig. 21C) has a thin cuticle on in the center. The xylem arrangement is simi- both epidermal surfaces. The upper epidermal lar to most of the other oaks, except that the PN-e529 FIGURE 21.—Willow oak {Quercus phellos L.)—Continued. D, Leaf midrib transection (X 103). E, Trunk periderm transection (X 74). F, Trunk phloem, cambium, and outer xylem (X 74). G, Trunk xylem transection (X 74). 58 upper tier of xylem is not divided into two Leaf shape and surface parts in this oak. A fiber tier encircles the The leaf is 10 to 18 cm long by 8 to 10 cm vascular bundle. A few rhombic crystals are wide with usually five deep lobes, alternate, present in cells just outside the fibers. In figure simple, deciduous, and leathery; the shape of 21D, part of a hair is present on the lamina. the apical lobe is obtuse or truncate ; the middle Stem transection lobes are almost square, giving a crosslike ap- The outer bark has thick, rough ridges and pearance to the leaf ; the base is wedge shaped. is nearly black on old trunks. It is a rhytidome The upper surface is dark green and smooth comprised of phellogens that produce both phel- with a variable concentration of appendages. lem to the outside and two or three phelloderm One leaf sampled had almost no hairs ; the leaf cells to the inside (fig. 21E). The outer living scanned in figure 22A had a moderate number secondary phloem is composed of abundant par- of tufted hairs. Also, it had capitate glands enchyma, many groups of large sclereids with with seemingly two-celled stalks and heads rhombic crystals, and some fibers. Many par- with four to eight cells. enchyma contain dark-staining materials, some The lower surface is light green and densely contain small clustered crystals. Some sclereid clusters are scattered; others occur more or less either in tangential lines or in radial lines from differentiated ray parenchyma. The trans- locating phloem (fig. 21F) is a tier of sieve elements up to about 10 cells adjacent to the cambium. Many of the ray parenchyma have differentiated into sclereids. The xylem is ring-porous (fig. 21G). Early wood vessels are large, usually two or three cells deep, and mostly broadly oval (66). Tran- sition from the large early wood to the small late wood vessels is gradual. Small late wood vessels are thick walled, almost round (fig. 21, F, G), and often are alined in radial rows. Abundant parenchyma are both paratracheal and apotracheal. Paratracheal parenchyma oc- cur around both early and late wood vessels. Some apotracheal parenchyma are diffuse, but some occur as one- and two-cell tangential lines between the rays, particularly in the late wood. Fibers are medium to thick walled, and many are gelatinous. Rays are of two kinds : (1) nar- row, mostly 1- or 2-seriate; and (2) broad, 10- to 35-seriate. Post Oak {Quercus stellata Wangenh.) Post oak, a member of the Leucobalanus sub- genus, occurs in all areas of Texas except the High Plains and the Trans-Pecos Mountains and Basins. It usually grows 15 to 23 m tall with a trunk diameter up to 6 dm. The crown is rounded with a few large branches. Post oak PN-5530 FIGURE 22.—Post oak (Quercus stellata Wangenh.). usually occurs on dry, upland sandy to claypan A, Leaf upper surface ( X 200). B, Leaf lower soils. surface (X 200). 59 PN-5531 FIGURE 22.—Post oak {Quercus stellata Wangenh.)- -Continued. C, Leaf lower surface stomata (X 1,005). D, Leaf lamina transection (X 323). E, Leaf midrib transection (X 85). F, Trunk periderm transection (X 85). covered with triehomes (fig. 22B). Trichomes Leaf transection consist mostly of tufted hairs with some multi- The lamina (fig. 22Z>) has a cuticle on both celled elongated glands. Stomata occur only on epidermises. Most upper and a few lower epi- the lower surface (fig. 22, B, C). Stomata are dermal cells are mucilaginous. The upper cells ranunculaceous, and a raised ridge entirely sur- are longer than the lower ones. Palisade paren- rounds the pore between the guard cells (fig. chyma are two or three cells deep ; the spongy 22C). parenchyma are loosely packed and contain 60 PN-5532 FIGURE 22.—Post oak (Qiiercus stellata Wangenh.)—Continued. G, Trunk phloem, cambium, and outer xylem transection (X 72). H, Trunk xylem transection {X 72). crystals. Many veins are vertically transcur- Both small and large clusters of sclereids arise rent. A tufted hair is present on the lower both from the phloem ground and ray paren- surface (fig-. 22D). chyma. The translocating phloem is 7 to 10 The midrib (fig. 22E) has a cylindrical, sieve elements wide and is split by a tangential superimposed xylem. Phloem appears to lie be- tier of fibers in this section (fig. 22G). tween the two tiers of xylem, as well as almost The xylem is ring-porous (fig. 22H) with surrounding the xylem. A tier of fibers almost large early wood vessels. In the inner rings, the completely surrounds the phloem and xylem. large vessels are filled with tyloses. Transition Rhombic and clustered crystals lie at the out- from the large early wood vessels to small, side edge of the fiber tier. thin-walled late wood vessels is abrupt. Both paratracheal and apotracheal parenchyma are Stem transection abundant. Paratracheal parenchyma occur The outer bark is gray to reddish brown and around both the large and small vessels. Some thick with vertical, deep fissures separating apotracheal parenchyma are diffuse, but most platelike ridges. The outer covering is a rhyti- form one-cell tangential bands, particularly in dome (fig. 22F) composed of phellogens that the late wood. Fibers are thick walled, and produce both phellem and phelloderm and cut some are gelatinous. Both narrow rays 1- to off tiers of nontranslocating phloem. Phello- 2-seriate and broad rays 10- to 30-seriate are gens form both tangential lines and curved present. Rhombic crystals are present in par- scales. Usually five to seven flattened phellem enchyma of both rays and tangential strands. cells are produced. Most are thin walled, but the cells in the youngest one or two layers are Live Oak (Quercus virginiana Mill.) frequently thick walled. The phelloderm is usu- ally two or three layers thick. The outer sec- Live oak occurs naturally in all areas of ondary phloem is composed of successive strata Texas except the High Plains and Trans-Pecos of parenchyma and sclerenchyma; Most paren- Mountains and Basins. Variable in shape, it chyma stain darkly. Sclerenchyma are present may grow to 18 m with a wide-spreading as fibers in more or less continual bands two crown, massive branches close to the ground, or three cells deep and as clusters of sclereids. and a trunk to 12 dm in diameter, or it may 61 PN~5533 FIGURE 23.—Live oak (Querem virginiana Mill.). A, Leaf upper surface ( X 220). B, Leaf lower surface ( X 200). C, Leaf lamina transection (X 85). D, Leaf midrib transection ( X 85). grow in dense thickets (running type) up to smooth because of a thick cuticle (fig. 23A). about 9 m tall. Live oak usually grows on sandy It contains no trichomes or stomata. The lower areas ranging from dry to moist sites. Also, it surface is light green and has many append- is commonly grown as an ornamental on upland ages (fig. 23ß). Most of the surface is covered sites. with stellate hairs, but a few capitate glands Leaf shape and surface are also present. Stomata are numerous and have raised lips on the guard cells around the The leaves are 5 to 13 cm long by 1.3 to 6.4 pore. cm wide, alternate, simple, persistent until new leaves appear; the shape is oblong, elliptical, Leaf transection or obovate, the apex broadly rounded to acute, The leaf lamina (fig. 23C) is thick and leath- the margin usually entire and curled, and the ery with a prominent cuticle on both surfaces. base cunéate to rounded. Upper epidermal cells are larger than the low- The upper leaf surface is dark green and er epidermal cells. Palisade parenchyma are 62 PN-6534 FIGURE 23.—Live oak (Quercus virginiana Mill.)—Continued. E, Trunk periderm transection {X 71). F, Trunk phloem, cambium, and outer xylem transection (X 71). G, Trunk xylem transection {X 71). elongated and two or three cells deep. The with shallow furrows and flat, scaly ridges. spongy parenchyma are loosely packed. Vein.s The outer area is a rhytidome composed of are vertically transcurrent with fibers both phellogens, with phellem and phelloderm cut- above and below most vascular bundles. ting off outer phloem (fig. 2SE). The outer The midrib (fig. 23Z>) has a central, super- secondary phloem is composed largely of par- imposed cylinder of xylem. The xylem levels enchyma with stratified tiers of fibers (fig. are separated by cells with medium-thick walls, 23F). Small to large clusters of sclereids are some of which are gelatinous. Phloem and fiber also present with occasional rhombic crystals. tiers lie outside the xylem. Clustered crystals The translocating phloem is a tier of about 10 are present in a few parenchyma just outside sieve elements deep and contains tangential the fibers. strata of fibers. The xylem is ring-porous but to a lesser de- Stem transection gree than other oaks (fig. 23G). The early The outer bark is reddish brown to black wood vessels are medium to small (fig. 23G), 63 and decrease in size gradually from early wood to late wood. The vessels have thick walls. Par- enchyma occur both paratracheally and apotra- cheally. Paratracheal parenchyma are rare and occur around the vessels. Apotracheal paren- chyma occur both as one to a few diffuse cells and also as wavy tangential lines one cell deep, particularly in the late wood. A few rhombic crystals are present in the tangential paren- chyma. Fibers are thick walled, abundant, and sometimes gelatinous. Both narrow rays 1- to 3-seriate and broad rays 10- to 30-seriate are present. Ulmaceae Sugarberry (Celtis laevigata Willd.) Sugarberry, or sugar hackberry, occurs in most areas of Texas. Gould (58) lists all areas except the Blackland Prairies. Correll and Johnston (30) list it growing in the eastern two-thirds of the state. It attains a height of 30 m with a spreading, round-topped or oblong crown. It grows largely in sandy, rocky, or alluvial soils in woodlands. Leaf shape and surface The leaves are 6 to 10 cm long by 2.5 to 5 cm wide, alternate, simple, and deciduous; the shape is lanceolate to ovate, the apex acumi- nate, the margin entire or a few teeth near the apex, and the base rounded and inequilateral (152). The upper surface is light green and papil- lose (fig. 24A). Trichomes include small bumps and long, tapering hairs. The veins are visible. The lower surface is light green with promi- nent veins (fig. 24B). Stomata occur only on the lower surface and are rubiaceous with a subsidiary cell parallel to the long axis of the pore outside each guard cell (fig. 24, B, C). Hairs on the lower surface are the same as noted for the upper surface. Leaf transection The leaf lamina (fig. 24D) has larger epi- PN-5535 dermal cells on the upper surface than on FIGURE 24.—Sugarberry {Celtis laevigata Willd.)- -A, the lower surface. Cuticle on both surfaces is Leaf upper surface (X 200). B, Leaf lower sur- thin. Palisade parenchyma are tightly packed face (X 200). C, Leaf lower surface {X 520). and two cells deep ; the spongy parenchyma are also tightly packed. Cystoliths in the epidermis 64 PN-5536 FIGURE 24.—Sugarberry {Celtis laevigata Willd.)—Continued. D, Leaf lamina transection (X 365). E, Leaf midrib transection (X 180). F, Trunk periderm transection (X 85). are associated with the base of many of the layers of thick-walled cells, some with rhombic hairs, but only on the upper surface {152). and clustered crystals, lies outside the phloem. Rhombic crystals are present in the bundle sheath of the vascular bundle. Fibers are also Stem transection present in the vascular bundle. The outer bark is light gray and is either In the midrib {fig. 24£'), the xylem is more smooth or covered with prominent corky warts. or less crescent shaped with a thick tier of The periderm consists of a phellogen with a phloem outside the xylem. A tier of one or two number of layers of phellem and phelloderm 66 PN-5537 FIGURE 24.—Sugarberry {Celtis laevigata Willd.)—Continued. G, Trunk phloem, cambium, and outer xylem (X 85). H, Trunk xylem transection (X 85). (fig. 2áF). The secondary, nontranslocating Leaf shape and surface phloem is composed of alternate tiers of paren- chyma and sclereids. The translocating phloem The leaves are 1.3 to 5.7 cm long by 1.3 to (fig. 24G) consists of only four to seven layers 2.5 cm wide, scabrous, alternate, simple, and of sieve elements before they are crushed be- deciduous ; the shape is elliptic to oblong-ovate, tween the parenchyma. Rhombic crystals occur three-nerved, the apex rounded to acute, the with the sclereids. margin entire to coarsely toothed, and the base oblique or semicordate. The xylem (fig. 2477) is ring-porous with The upper surface is dark green and almost several (two to five) layers of early wood ves- smooth (fig. 25A). Many short, thick, slightly sels. Some early wood vessels in the older rings rough hairs are present. The lower epidermis contain tyloses. Transition from early wood is slightly papillose (fig. 25ß). The veins are vessels to late wood vessels is more or less ab- prominent (not in photo). Two types of pointed rupt. Late wood vessels are small, numerous, hairs are present, some are short and others and arranged in somewhat concentric bands. are medium long and pointed. Ranunculaceous Paratracheal parenchyma that join the early stomata occur only on the lower surface and lie wood vessels are abundant. The apotracheal even with the ground epidermal cells. parenchyma are sparsely scattered among the fibers. The fibers are thick walled and fre- Leaf transection quently gelatinous. The rays are mostly five- to eight-seriate. On the lamina (fig. 25C), the cuticle is thin. The upper epidermal cells are larger than the Granjeno {Celtis pallida Torr.) lower ones. Palisade parenchyma are mostly two cells deep. Spongy parenchyma are tightly Granjeno, or spiny hackberry, occurs in the packed in this sample but were loosely packed Gulf Prairies and Marshes, South Texas Plains, in another study (152). Cystoliths occur under Edwards Plateau, and Trans-Pecos Mountains both surfaces and are associated with both the and Basins of Texas. It is a spiny, spreading, ground cells and hairs. Some of the epidermal densely branched evergreen shrub attaining a and mesophyll cells contain mucilage. Vascular height of 5.5 m. It occurs largely on dry, clayey, bundles are sheathed by large parenchyma cells. and gravelly soils. In the midrib (fig. 250), the xylem is crescent 66 PN-5B38 FIGURE 25.—Granjeno (Celtis pallida Torr.). A, Leaf upper surface (X 200). B, Leaf lower surface (X 200). C, Leaf lamina transection (X 318). Z), Leaf midrib transection (X 85). shaped and lies above a tier of phloem. A num- The outer phloem (fig. 25, E, F) is composed ber of mesophyll cells are mucilaginous. of parenchyma, crushed sieve elements, and groups of large sclereids. Rhombic crystals are Stem transection present among the sclereids. Fibers are sparse The outer bark is mottled gray to reddish and occur in short, discontinuous tiers. The brown and rather smooth with long, stout, gray translocating phloem, adjacent to the cambium, or brown spines. The bark is only rough at the is about 10 cells deep. base of old trunks. The phellogen produces phel- The xylem is diffuse-porous (fig. 25, F, G). lem to the outside and phelloderm to the inside Vessels occur either singly or in more or less (fig. 2bE). radial files of up to four cells. Both paratra- 67 PN-5539 FIGURE 25.—Granjeno {Celtis pallida Torr.)—Continued. E, Trunk periderm and outer phloem transection (X 75). F, Trunk phloem, cambium, and outer xylem (X 75), G, Trunk xylem transection (X 75). cheal and apotracheal parenchyma are present. Prairies. It is a spring-blooming elm that grows The paratracheal parenchyma are two to four to 18 m tall with slender branches having corky cells deep surrounding the vessels. The apotra- wings. The crown is round or oblong. It grows cheal parenchyma occur both to connect the both on dry upland, particularly with post oak vessels as bands usually two to four cells wide and blackjack oak, and moist lowland sites. and as isolated diffuse areas. Fibers are thick walled and many are mucilaginous. Rays are Leaf shape and surface one- to three-seriate. The leaf is 1.3 to 8 cm long by 0.6 to 3.8 cm wide, alternate, simple, and deciduous; the Winged Elm (Ulmus alata Michx). shape is ovate-oblong to oblong-lanceolate, the Winged elm occurs in the Pineywoods, Gulf apex acute or acuminate, the margin coarse- Prairies and Marshes, Post Oak Savannah, ly doubly serrate, and the base rounded to Blackland Prairies, and Cross Timbers and subcordate. 68 PN-5540 FIGURE 26.—Winged elm {Ulmus alata Michx.). A, Leaf upper surface (X 120). B, Leaf lower surface (X 110). C, Leaf lower surface stomata and trichomes (X 550). D, Leaf lamina transection (X 230). The upper surface is shiny, dark green. The Leaf transection surface of the ground epidermal cells is smooth, The lamina (fig. 26Í)) has a prominent cuti- but small, tapered, nonglandular hairs are com- cle on the upper epidermal cells. The upper mon (fig. 26A). The lower surface is almost epidermal cells are larger than the lower epi- smooth with prominent veins (fig. 26B). Many dermal cells, and some cells of both surfaces solitary nonglandular hairs are present, and are mucilaginous (152). The palisade paren- they are longer than those on the upper sur- chyma are one or two cells deep. Spongy par- face. Also, a few glandular hairs (fig. 26, B, enchyma are loosely packed. Most veins are C) are present with short stalks and multi- vertically transcurrent and have fibers. celled heads. Numerous hairs are present on the midrib and large veins. Ranunculaceous The midrib (fig. 2QE) has a crescent-shaped stomata occur only on the lower surface. The xylem with successive layers of phloem and surfaces of the guard cells are raised above fibers to the outside. Some rhombic crystals the level of the ground epidermal cells with the are present in parenchyma just outside the inner surface angled downward toward the fibers. The epidermis contains an abundance of pore. Wax partially covers many of the pores. nonglandular hairs. 69 PN-5541 FIGURE 26.—Winged elm {XJlmiis alata Michx.)—Continued. E, Leaf midrib transection (X 128). F, Trunk peri- derm transection (X 85). G, Trunk phloem, cambium, and outer xylem transection (X 85). H, Trunk xylem transection (X 85). 70 Stern transection Some marginal parenchyma are usually pres- The outer bark is reddish brown to gray with ent. Apotracheal parenchyma among the fibers shallow, irregular fissures separating flat, scale- are sparse. Fibers are mostly thick walled and like ridges. The outer covering is a rhytidome gelatinous. Rays are three- to five-seriate. composed of several phellogens that arise in the secondary phloem and produce numerous layers Cedar Elm (Ulmus crassifolia Nutt.) of phellem to the outside and about six phello- Cedar elm occurs in all areas of Texas except derm cells to the inside (fig. 26F). Outer non- the Rolling Plains, High Plains, and Trans- translocating phloem (fig. 26, F, G) consists of Pecos Mountains and Basins. It grows to 27 m more or less stratified layers of dark-staining tall with a narrow to round crown. It often parenchyma separated by smaller-diameter occurs on limestone soils on open slopes but fibers. Also, individual and small clusters of may occur in low-lying woodlands. sclereids, some with rhombic crystals, are pres- Leaf shape and surface ent. Translocating phloem (fig. 26G) consists of similar tissues as the nontranslocating The leaves are 2.5 to 5 cm long by 1.9 to 2.5 phloem, except the active sieve elements are cm wide, alternate, simple, and tardily decid- present individually to groups up to about 10 uous ; the shape is elliptic to ovate, the apex cells. acute to obtuse, the margin doubly serrate, and The xylem is ring-porous (fig. 26ÍÍ). Early the base rounded or cunéate to oblique. wood vessels are medium sized, spaced more or The upper leaf surface is dark green, stiff, less irregularly along the growth ring, and and rough to the touch. It is rather smooth separated by smaller vessels. Early wood ves- over the ground epidermal cells. Apparently, sels grade gradually in size to the late wood the roughness arises from the sparse, short, vessels. Small late wood vessels mostly occur in tapered nonglandular hairs (fig. 27A). groups arranged in more or less continuous The lower surface is lighter green than the wavy tangential bands ; however, some are upper surface and has prominent veins (fig. either solitary or in clusters {152). Para- 27ß). The lower surface is undulating and has tracheal parenchyma are abundant, partially numerous trichomes. Trichomes consist of num- surrounding the larger early wood vessels, and erous long, pointed nonglandular hairs and more or less surrounding the small early wood short-stalked glandular hairs. Most of the vessels and wavy bands of late wood vessels. stalked hairs are partially collapsed on this leaf PN-5542 FIGURE 27.—Cedar elm (t/imMs crassi/oiia Nutt.). A, Leaf upper surface (X 220). B, Leaf lower surface (X 220). 71 PN'B543 FIGURE 27.—Cedar elm iUlmiis crassifolia Nutt.)—Continued. C, Leaf lamina transection (X 315). D, Leaf mid- rib transection (X 94). (fig. 21B). Ranunculaceous stomata are pres- early wood vessels being slightly larger than ent only on the lower surface. Surfaces of the the late wood vessels (fig. 27G). Early wood guard cells are raised above the level of the vessels are solitary or in small groups of two ground epidermal cells with the inner surface or three, mostly in radial files. Late wood ves- angled downward toward the pore. Cuticle sels arise in groups lying more or less in wavy partially covers some of the pores. bands. Sweitzer (152) found some tyloses in the vessels. Vessel elements usually have simple Leaf transection perforation plates, but some bear vestigial The lamina (fig. 27C) has a prominent scalariform plates {160). Parenchyma are cuticle on both surfaces. Upper epidermal cells mostly paratracheal around the outer side of are larger than the lower ones. Most of the the larger early wood vessels at the ring and upper and a few of the lower epidermal cells completely around the other vessel groups. are mucilaginous. Palisade parenchyma are Fibers are medium to thick walled and abun- mostly one cell deep; spongy parenchyma are dant, particularly in the late wood; some are fairly loosely packed. Veins are vertically trans- gelatinous. Most rays are three- to six-seriate. current. The midrib (fig. 270) has a crescent- shaped xylem above successive tiers of phloem Moraceae and fibers. Osageorange Stem transection [Madura pomífera (Raf.) Schneid.] The outer bark is brown to gray with flat- tened ridges broken into thin loose scales. The Osageorange grows in all areas of Texas ex- phellogen produces numerous layers of phellem cept the South Texas Plains and the High to the outside and about six layers of phello- Plains. It grows to a spiny tree 18 m. tall with derm to the inside (fig. 27E). Outer nontrans- a diameter of 6 to 9 dm and a crown rounded locating phloem is stratified into layers of and open. Osageorange may also occur as dark-staining parenchyma and fibers (fig. 27, thickets. It usually grows at the edge of fields E, F). Translocating phloem (fig. 27F) con- and as fence rows both on upland and most tains tissue similar to the nontranslocating lowland soils. phloem but with scattered solitary to small groups of sieve elements. Leaf shape and surface The xylem is semiring-porous with most The leaves are 8 to 15 cm long by 5 to 10 cm 72 PN-5544 FIGURE 27.—Cedar elm (Ulmus crassifolia Nutt.)—Continued. E, Trunk periderm transection (X 85). F, Trunk phloem, cambium, and outer xylem (X 85). G, Trunk xylem transection (X 85). 73 PN-B545 FIGURE 28.—Osageorange {Madura pomífera (Raf.) Schneid.]. A, Leaf upper surface (X 210). B, Leaf lower surface (X 210). C, Leaf lamina transection (X 225). D, Leaf midrib transection (X 85). wide, alternate, simple, and deciduous; the ular hairs occur mainly on the prominent veins. shape is broad-ovate to elliptic-lanceolate, the Usually many more hairs are present on the apex acuminate, the margin entire, and the base lower surface, particularly on the veins, than rounded or subcordate. on the upper surface. Ranunculaceous stomata The upper surface is dark green, shining, occur only on the lower surface and are slightly and slightly papillose from wax or cuticle de- elevated above the ground epidermal cells. posits {fig. 28A). Veins are prominent with a scattering of long, pointed nonglandular hairs. Leaf transection The lower surface is lighter green than the The lamina (fig. 28C) contains large epi- upper. Epidermal cells are papillose (fig. 2SB). dermal cells. Palisade parenchyma are one or Long nonglandular and short-stalked gland- two cells deep; spongy parenchyma are loosely 74 PN-5546 FIGURE 28.—Osageorange IMaclura pomífera (Raf.) Schneid.]—Continued. E, Trunk periderm transection (X 68). F, Trunk phloem, cambium, and outer xylem transection (X 68). G, Trunk xylem transection {X 68). packed. Most medium-sized veins are vertically yellow to brown and deeply furrowed with flat transcurrent with larg'e, thin-walled sheathing- ridges {68). It is a rhytidome composed of cells. The smallest veins lie at the junction of numerous phellogens that produce three to the palisade and spongy parenchyma. eight layers of phellem (fig. 2%E). The second- The midrib (fig. 28i>) contains a crescent- ary phloem between the phellogens consists shaped xylem. Phloem almost completely en- largely of crushed parenchyma and laticifers. circles the xylem. A number of parenchyma Fibers are sparse, and a few rhombic crystals outside the vascular bundle contain clustered are present. Translocating phloem (fig. 28F) crystals. Several thin-walled cells, probably contains prominent sieve elements separated laticifers, are present among the parenchyma. by two strata of parenchyma. Some paren- Also, entire hairs and sections of several hairs chyma are heavily pitted and some contain are present on the epidermis. crystals {93). Laticifers are scattered through- out the phloem. Stem transection The xylem is ring-porous (fig. 28G) and The seasonal development of the shoot apex light yellow {68). Early wood vessels are large has been described by Smith {137). In the and one to three celh deep. Tyloses are common mature tree, the outer bark is dark orange or with vessels of the heartwood being completely 75 "—%• 4 PN-5547 FIGURE 29.—Red mulberry (Morus rubra L.). A, Leaf upper surface (X 230). B, Leaf lower surface (X 200). C, Leaf lamina transection (X 180). occluded. The transition from early wood to small tree 6 to 12 m high with a trunk 2 to late wood vessels is abrupt. Late wood vessels 3.8 dm in diameter and has a round-topped are small and arranged in small groups often crown. It may, however, grow to 21 m tall. It coalescing into more or less tangential, wavy usually grows as an understory species on rich, bands. Paratracheal parenchyma are abundant, moist sites. encircling and interconnecting the early and Leaf shape and surface late wood vessels. Some marginal parenchyma also occur in a discontinuous line along the Leaves are 8 to 23 cm long, alternate, simple, growth ring. Fibers are thick walled and and deciduous; the shape is oval or ovate, un- mosty gelatinous. Rays are one- to six-seriate lobed or deeply one- to three-lobed, the apex wide, but most are two- to four-seriate. long acuminate, the margin coarsely serrate, and the base truncate or cordate. Red Mulberry (Morus rubra L.) The upper surface is dark green and usually rough. The ground epidermal cell surfaces are Red mulberry grows in all areas of Texas papillose. Both long and short hairs are except the High Plains and the Trans-Pecos present, but widely scattered (fig. 29A). Mountains and Basins. It usually grows to a The lower surface is paler and softer to the 76 PN-5548 FIGURE 29.^Red mulberry (Morus rubra L.)^Continued. D, Leaf midrib transection (X 85). E, Trunk periderm and outer phloem transection (X 85). touch than the upper surface. Epidermal cell Large crescent-shaped xylem and phloem tiers surfaces are also slightly papillose (fig. 29B). are located centrally. Above these are three Numerous trichomes are present. Nonglandular small vascular bundles with phloem around hairs vary from short ones with wide bases to most of the xylem. long, pointed ones. Many glandular hairs with Stem transection multicelled heads are present, particularly on the veins. Ranunculaceous stomata occur only The outer bark is dark brown to gray, thin, on the lower surface and are slightly elevated and with elongated plates. It is a rhytidome above the plane of the ground epidermal cells. composed of several phellogens cutting off tiers of old, nontranslocating phloem that is now Leaf transection mostly sclereids with a few parenchyma, latici- The lamina (fig. 29C) has a thin cuticle. fers, and fibers (fig. 28E). Phellogens produce Upper epidermal cells are larger than the lower 5 to 20 layers of phellem. Secondary phloem ones. The inner half of a few of the upper epi- consists mostly of parenchyma with some scler- dermal cells are mucilaginous. Cystoliths are eids, fibers, and laticifers. The translocating scattered among the upper epidermal cells. phloem (fig. 29F) is composed of large sieve Palisade parenchyma are one cell deep ; spongy elements separated by more or less continuous parenchyma are moderately well packed. Most tangential strata containing both parenchyma veins are vertically transcurrent with large and fibers. sheathing parenchyma cells. The xylem is ring-porous (fig. 29G) {160). The midrib (fig. 29/)) has a large amount of Early wood forms a band two to eight vessels parenchyma. The vascular system is complex. deep. The transition from early to late wood is 77 PN-5549 FIGURE 29.—Red mulberry {Moms rubra L.)—Continued. F, Trunk phloem, cambium, and outer xylem transection (X 85). G, Trunk xylem transection (X 85). usually abrupt {6Jf). Late wood vessels (fig. Leaf shape and surface 29F) are small, either solitary or nested in The leaves are 5 to 10 cm long, alternate, small groups, often forming more or less wavy palmately compound, three-foliolate, and ever- tangential bands. Parenchyma are almost en- green. Leaflets are 2.5 to 6 cm long by 1.3 to tirely paratracheal around the vessels. Fibers 3.8 cm wide; the shape is elliptic to narrowly are thin to thick walled and frequently gelati- lanceolate, the apex acuminate and spiny, the nous. Rays are one- to eight-seriate, and most margin three- to seven-lobed and spiny pointed, are three- to five-seriate. and the base acute. The upper leaflet surface is grayish green Berberidaceae with white veins. The upper surface is highly Agarito {Berberís trifoliolata Moric.)^ papillose from rows of protuberances running parallel to the long axis of the leaflet (fig. Agarito occurs in all areas of Texas except BOA). the Blackland Prairies and the High Plains. The lower surface is lighter green than the It is a shrub growing to 3 m tall with rigid upper surface. Veins have a slight papillose ascending or spreading branches. It grows on surface with rows of protuberances lying paral- dry, stony hillsides and flats of pastures, lel to the vein (fig. 30ß). The lamina is highly thickets, and open woods. corregated with deeply sunken stomata (fig. 30, B, C). Ranunculaceous stomata occur only -> Synonymous with Mahonia trifoliolata (Moric.) on the lower surface. No trichomes were found Fedde (3,171). on either surface. 78 PN-5550 FIGURE 30.—Agarito (Berberís ín/oíio/o.í(i. Moric.). ^, Leaf upper surface (X 220). ß. Leaf lower surface (X 220). C, Leaf lower surface stomata ( X 550). D, Leaf lamina transection ( X 222). Leaflet transection increases to about five at the leaf margin. The In the lamina (fig. 300), a thick cuticle is spongy parenchyma are loosely packed. The present on both epidermises. Protuberances on unevenness of the lower surface is caused by the upper surface seem to arise largely from extensions of the epidermal cells. The larger the uneven thickness of the cuticle. Also, the veins are vertically transcurrent and include cuticle extends downward almost to the base fibers and rhombic crystals. Small veins lie in around the upper epidermal cells. Two or three the spongy parenchyma, and they have a sheath layers of fibers lie beneath the upper epidermis. of parenchyma, many of which contain rhombic In the lamina, the palisade parenchyma are crystals. two or three cells deep, similar to Mahonia One vascular bundle occurs in the midrib aquifolia {13) ; however, the number of fibers (fig. Z()E) and consists of a circular xylem 79 PN-5551 FIGURE 30.—Agarito (Berberís trifoHolata Moric.)—Continued. E, Leaf midrib transection (X 79). F, Trunk periderm transection {X 79). G, Trunk phloem, cambium, and outer xylem (X 79). H, Trunk xylem transec- tion (X 79). with a crescent-shaped tier of phloem below. chyma in two or three tiers between tiers of The bundle is surrounded by fibers that are fibers. Sieve elements to the outside are vertically transcurrent to both epidermises. subsequently crushed. Stem transection The xylem is diffuse- to semiring-porous (fig. 30iî). Early and late wood vessels are The outer bark is gray to reddish brown and broken into thin, small scales. It is made up of small. A continuous tier of vessels lies on the continuous layers of secondary phloem com- ring, and some vessels are only slightly larger posed of stratified layers of parenchyma and than those subsequently produced. Most vessels fibers plus sclereids (fig. 30F). Some sclereids are arranged in irregular clusters with a tend- have rhombic crystals. ency to be grouped in wavy bands. Parenchyma The translocating phloem (fig. 30G) is com- appear to be absent. Fibers are mostly thick- posed of small sieve elements among paren- walled. Rays are 6- to 16-seriate. 80 PN-5B52 FIGURE 31.—Southern magnolia (Magnolia grandiflora h.). A, Leaf upper surface (X 198). B, Leaf lower surface {X 198). C, Leaf lamina transection (X 99). D, Leaf midrib transection (X 41). Magnoliaceae the shape is elliptic to oval, the apex acute to acuminate, the margin entire, and the base Southern Magnolia cunéate. (Magnolia grandiflora L.) The upper surface is smooth, lustrous, and bright green (fig. 31A). The lower surface Southern magnolia occurs in the Pineywoods appears reddish brown and pubescent from the and Gulf Prairies and Marshes of Texas. It numerous curled, long, pointed nonglandular usually grows to a tree 24 m tall with a straight hairs on the lamina, midrib, and veins (fig. trunk 6 to 0 dm in diameter with a pyramidal- 31J5). Many hairs have an enlarged collar in ly shaped crown. Southern magnolia grows the middle and are often twisted. Stomata are mostly on rich; moist lowland soils (65). How- numerous, large, and rubiaceous with two sub- ever, it is grown as an ornamental on upland sidiary cells. The upper surface of the guard sites. cells lies above the plane of the ground epi- dermal cells. Many have wax or other material Leaf shape and surface partially covering the pore. Stomata are absent The leaves are 10 to 23 cm long by 5 to 8 cm along the margins and from the veins (107, wide, alternate, simple, evergreen, and stiff; 109). 81 PN-5653 FIGURE 31.—Southern magnolia (Magnolia grandiflora L.)—Continued. E, Trunk periderm transection (X 85). F, Trunk phloem, cambium, and outer xylem transection {X 85). G, Trunk xylem transection (X 85). 82 Leaf transection erect branches. It grows in sandy to rich soils The lamina (fig. 31C) has a prominent of river bottoms and swamps (66). cuticle on both epidermises. Upper epidermal Leaf shape and surface cells seem to contain oil globules as reported Leaves are 8 to 10 cm long by 2.5 to 4.6 cm by Pant and Gupta (109). A hypodermis, one wide, alternate, simple, persistent, aromatic, cell thick, lies below the upper epidermis. and stiff; the .shape is lanceolate to elliptic, the Lower epidermal cells are smaller than the apex acute or acuminate, the margin entire, upper ones. Palisade parenchyma are two or and the base wedge shaped. three cells deep ; spongy parenchyma are loose- The upper surface is bright green and lus- ly packed. Large cells, presumably secretory trous. The surface is slightly papillose and cells, occur among both types of parenchyma. contains a few long nonglandular hairs (fig. Veins are vertically transcurrent. 32A). In the midrib (fig. 31Z)), the vascular tissue The lower surface is lighter green than the is arranged in a circular series of vascular upper surface. Epidermal cells are prominently bundles. Successive tiers of phloem and fibers papillose (fig. 32ß). Long, tapering, rusty-red lie outside the xylem. Pithlike parenchyma fill nonglandular hairs are abundant, particularly the center. along the veins (178). Stomata are numerous. Stem transection The outer bark is thin, gray to dark brown, and with shallow fissures separating narrow scaly ridges. Shallow forming phellogens pro- duce 7 to 20 layers of phellem (fig. SIS') over nontranslocating secondary phloem consisting of parenchyma, fibers, and clusters of sclereids. Translocating phloem (fig. 31F) consists of groups of large sieve elements separated by more or less tangential tiers of fibers. Secre- tory cells are common among parenchyma in the phloem. Rays tend to enlarge from the cambium outward ; the increased width arises from both cell enlargement and additional numbers of cells. The xylem is diffuse-porous (fig. 31G) (65). Vessels are small and quite uniform in size, and have spiral thickenings and scalariform perforation plates (14-5, 153). Most vessels occur in radial lines. Parenchyma are almost entirely marginal along the growth ring in a tier one to five cells deep, making the growth rings prominent (23). Fiber tracheids are moderately thin walled. Rays are one- to five- seriate, with most being two- to four-seriate. Lauraceae Redbay [Persea horbonia (L.) Spreng.] Redbay occurs in the Pineywoods and Gulf Prairies and Marshes of Texas. It is a medium- sized tree growing to 15 m, occasionally to PN- 5554 FIGURE 32.—Redbay \_Persea borbonia (L.) Spreng.]. 21 m tall, with a trunk diameter 3 to 6 dm. A, Leaf upper surface (X 174). B, Leaf lower The crown is short and pyramidal, having stout, surface (X 166). 83 PN 55üG FIGURE 32.—-Redbay [Persea borbonia (L.) Spreng.]—Continued. C, Leaf lamina transection (X 235). D, Leaf midrib transection {X 80). E, Trunli periderm and outer phloem transection (X 85). F, Trunli phloem, cambium, and outer xylem transection (X 85). G, Trunk xylem transection (X 85). 84 occurring only on the lower surface, and are dark-staining parenchyma and thick-walled rubiaceous. fibers. The xylem is semiring- to diffuse-porous Leaf transection (fig. 32G). Vessels are small to medium sized, The lamina (fig. 32C) has a prominent cuti- occurring either singly, in radial files up to cle on both epidermises. Palisade parenchyma five cells, or occasionally in clusters of three to are one to three cells deep ; spongy parenchyma six. Early wood vessels are slightly larger than are loosely packed. Numerous large, spherical, late wood vessels. Parenchyma are primarily thin-walled oil or secretory cells occur both in paratracheal, either completely or almost com- the paHsade and spongy parenchyma. Oil cells pletely surrounding the vessels in one or two often have suberized walls and yellow contents. layers. A few parenchyma are apotracheal, oc- Veins are normally vertically transcurrent and curring as scattered cells among the fibers. often contain fibers. Fibers are mostly thick walled and generally The midrib (fig. 32D) is oval with a central, gelatinous. Rays are typically one- to three- slightly crescent-shaped xylem. A tier of seriate. phloem lies under the xylem, and a tier of fibers almost completely surrounds the vascu- Sassafras lar tissue. A few cells in the parenchyma [Sassafras albidum (Nutt.) Nees] region seem to be secretory cells. Sassafras grows in the Pineywoods, Gulf Stem transection Prairies and Marshes, and Post Oak Savannah The outer bark is thin, reddish to grayish areas of Texas. It is usually a shrub to a medi- brown, and scales are separated by thin fur- um-sized dioecious tree 6 to 15 m tall, but it rows {66). Phellogens arise near the surface may grow to 27 m. Sassafras usually grows on producing both phellem and phelloderm (fig. sandy areas in old fields, along fence rows, and S2E). Phellogens cut off a little secondary at the edge of woods. phloem containing parenchyma and sclereids to Leaf shape and surface form a rhytidome. Some of the phelloderm also form sclereids. The outer secondary phloem The leaves are 8 to 15 cm long by 2.5 to 13 cm (fig. 32, E, F) contains mostly large paren- wide, alternate, simple, and deciduous; the chyma with solitary or small groups of large shape is ovate or elliptic with three common and small sclereids. Translocating phloem (fig. forms: (1) unlobed, (2) mitten shaped (two- 32F) contains sieve elements separated by lobed), or (3) three-lobed. The apex is acute PN-ñ55fi FIGURE 33.—Sassafras {Sassafras albidum (Nutt.) Nees]. A, Leaf upper surface (X 200). B, Leaf lower surface (X 200). 85 PN-5557 FIGURE 33.—Sassafras \_Sassafras albidum (Nutt.) Nees]—Continued. C, Leaf lamina transection (X 312). D, Leaf midrib transection (X 77). E, Trunk periderm transection (X 78). to obtuse, the margin is entire (not considering ent at the upper right; the darkened spots lobing), and the base wedge shaped. appear yellowish and almost translucent with The upper surface is dull dark green. It is transmitted light. papillose with scattered long, tapering non- Leaf transection glandular hairs (fig. 33A). The lower surface is lighter green and has numerous long non- The lamina (fig. 33C) has a prominent cuti- glandular hairs (fig. 33ß). The ground epi- cle on the upper surface. Epidermal cells are dermal cells are papillose. Stomata occur only irregularly shaped. The upper epidermal cells on the lower surface and are rubiaceous. A are often larger than the lower ones. Palisade secretory cell underlying the epidermis is pres- parenchyma are one or two cells deep; spongy 86 PN-5558 FIGURE 33.—Sassafras {Sassafras albidum (Nutt.) Nees]—Continued. F, Trunk phloem, cambium, and outer xylem (X 85). G, Trunk xylem transection {X 85). parenchyma are loosely packed. Oil secretory by strata of thick-walled fibers surrounded by cells are almost entirely in the palisade paren- dark-staining parenchyma. chyma of the lamina. Most of the veins are The xylem is ring-porous (fig. 33, F, G). vertically transcurrent, and the larg^er ones Early wood vessels are large, one to three cells contain fibers. deep, and grade abruptly to small late wood The midrib (fig. ZW) has a slightly cres- vessels. Late wood vessels are small, round to cent-shaped xylem above a crescent-shaped tier ovate, and thick walled ; about 84 percent are of phloem. Some small thick-walled fibers lie mostly solitary and 15 percent are in radial both above and below the vascular bundle. groups of two or three cells, according to Stern Some secretory cells are present among the {1U7). Vessels rarely occur in clusters. Paren- parenchyma. A long hair grows from the chyma are paratracheal, at least partially sur- epidermis on the left side. rounding the vessels. Parenchyma tiers are usually one or two layers wide around the ves- Stem transection sels. Fiber tracheids are thin walled. Rays are The outer bark is reddish brown to gray, mostly one- to three-seriate, and a few contain aromatic, and irregularly broken into flat oil cells. ridges. It is a rhytidome. Several phellogens form in the outer secondary phloem (fig. 33Í7). Hamamelidaceae Thin-walled phellem is produced to the outside. Sweetgum (Liquidambar styraciflua L.) The phelloderm appears to be mostly sclereids. Nontranslocating phloem is composed mostly of Sweetgum grows in the Pineywoods, Gulf parenchyma with groups of large sclereids. Prairies and Marshes, and Post Oak Savannah The translocating phloem (fig. 33F) is made of Texas. It attains a height of 25 to 45 m with up of a tier of 6 to 10 sieve elements separated a trunk 6 to 12 dm in diameter. Sweetgum is 87 PN-5569 FIGURE 34.—Sweetgum (Liquidamhar styraciflua L.). A, Leaf upper surface (X 550). B, Leaf lower surface (X 650). C, Leaf lower surface marginal gland (X 190). D, Leaf lamina transection (X 230). normally a dominant or codominant tree that and are rubiaceous. Some long, pointed hairs prefers growing on rich, bottom-land soils, al- are present on the lamina and veins ; many though it does grow on some sandy upland occur at the junction of the veins. sites with pines. Leaf transection Leaf shape and surface The cuticle on both epidermal surfaces is thin The leaves are 8 to 23 cm in diameter, al- (fig. 34/)). Upper epidermal cells are generally ternate, simple, deciduous, star shaped or orbic- larger than lower ones. Palisade parenchyma ular, three- to seven-lobed, and palmately are usually two cells deep ; spongy parenchyma veined ; the apex of each lobe is acuminate, the are loosely packed. The vein is vertically margin finely serrate, and the base truncate or transcurrent with a circular vascular bundle. slightly cordate. Leaf shape is highly variable A large secretory canal is present in the xylem. Clustered crystals are common among the The upper surface is lustrous and bright spongy parenchyma. green. The surface is slightly papillose with The midrib (fig. SiE) has a cylindrical fine wax striations (fig. 34A). The lower sur- xylem and phloem. Two secretory canals are face is also slightly papillose and paler green inside the xylem. Medium thick-walled cells, (fig. 34B). Glands occur on the leaf teeth (fig. which are probably fibers, lie in a discontin- 34C). Stomata occur only on the lower surface uous tier outside the phloem. A few clustered 88 .- *' -' '- '>■ iß^9 • ^ PN-B560 FIGURE 34.—Sweetgum (Liquidambar styraciflua L.)—Continued. E, Leaf midrib transection (X 80). F, Trunk periderm transection (X 80). G, Trunk phloem, cambium, and outer xylem transection (X 80). H, Trunk xylem transection (X 80). crystals are present among the parenchyma four layers of phelloderm to the inside of the below the vascular bundle. phellogen (25). Some tangential bands of phel- lem cells are narrow and thick walled. Some Stem transection discontinuous bands of sclereids arise among The outer bark is gray, gray brown, or the phellem.. purplish brown and thick with deep furrows The outer, nontranslocating phloem consists separating narrow, rounded, sometimes flaky of parenchyma and discontinuous tiers contain- ridges. In vigorous trees the bottoms of the ing fibers and sclereids (fig. 34G). Both furrows display streaks of light inner bark. rhombic and clustered crystals are present. The bark is a rhytidome with thick tiers of Many parenchyma cells are tanniferous. The phellem to the outside (fig. 34F) and two to translocating phloem consists of a tier about 6 89 PN 55 Ül FIGURE 35.—American sycamore (Platanus occidentalis L.). A, Leaf upper surface (X 200). B, Leaf lower sur- face with vein (X 200). C, Leaf lower surface with hair (X 210). to 10 sieve elements wide. Also, numerous fiber tracheids. Fiber tracheids are moderately groups of fibers and sclereids, similar to the thick walled. Rays are one- to four-seriate. outer phloem, form discontinuous strata. Paren- chyma are diffuse among the sieve elements, Platanaceae and most are tanniferous. Chang (25) found American Sycamore some parenchyma formed four to six more or (Platanus occidentalis L.) less continuous tangential bands with one to three cells of parenchyma in the living phloem. American sycamore grows in all areas of The xylem is diffuse-porous (fig. 34/7) (6^). Texas except the Rolling Plains, High Plains, Vessels are numerous, small, and either solitary and Trans-Pecos Mountains and Basins. It or in radial groups of up to six cells ; most occur grows to 21 to 50 m tall with a trunk 9 to in groups of two or three cells. The vessels 33 dm in diameter. The crown is open. Ameri- are thin walled and have spiral thickenings at can sycamore grows in open areas as a scat- the tapering ends. Perforation plates are tered tree or in small groves, particularly on scalariform v/ith 15 or more bars. Parenchyma moist sites. The tree is frequently used as an are scanty around the vessels and among the ornamental. 90 Leaf shape and surface The leaves are 10 to 18 cm in diameter, thin and firm, alternate, simple, and deciduous; the shape is broadly ovate with three to five lobes, the apex acuminate, the margin of lobes either entire or with a few long, pointed teeth, and the base truncate or cordate. The upper surface is bright green. It is smooth except for fine wax striations and oc- casional candelabra hairs particularly on the veins and midrib (fig. 35Ä). The lower surface {fig. 35ß) has prominent veins. Epidermal cells are papillose. Stomata are ranunculaceous and are somewhat raised above the ground epidermal cells. Many can- delabra hairs occur on the lower surface (fig. 35C), particularly at the junctions of the mid- rib and main veins. Many break off as shown by the stumps on the vein (fig. 35B). Also, a few capitate glands are present as shown at the lower right-hand corner. Leaf transection In the lamina (fig. 35Z>), the cuticular layers are thin. Palisade parenchyma are one cell thick; spongy parenchyma are loosely packed. Some spongy parenchyma are somewhat verti- cally elongated, but they are not as long as the ■^•\ palisade parenchyma. Most veins are vertically à O .- transcurrent, and the larger ones contain "^v fibers. In the midrib (fig. SöE"), the xylem is highly complex. A crescent-shaped tier lies from the •"^\.,;jä bottom up about half way on either side. Two ■* c>- more or less vertical arcs of xylem lie at the ^í top. Phloem lies below the lower arc of xylem and inside the two vertical arcs of xylem. A tier of fibers completely encircles the vascular .TTft-. ,,-'.^ bundle. Stem transection The outer bark is thin and characteristically PN-5562 mottled brown and white or greenish white on FIGURE 35.—American sycamore (Platanus occidentalis the upper trunk by exfoliating outer layers that L.)—Continued. D, Leaf lamina transection (X expose the lighter colored inner layers. The 345). E, Leaf midrib transection (X 85). lower trunk is reddish brown and scaly. A phellogen forms deep in the secondary phloem the outer bark being much thinner than the and produces phellem to the outside and phello- inner surface. In late summer, the isolated sec- derm to the inside (fig. 35f ). The outer ondary phloem and thin-walled phellem strip phellem cells are thin walled and about of equal off at the transition between the two types of thickness. The inner three to five layers have phellem (25). Usually three to five layers of simple pits and thick walls with the side facing phelloderm form. 91 PN'55fi3 FIGURE 35.—American sycamore {Platanus occidentalis L.)—Continued. F, Trunk periderm transection (X 67). G, Trunk phloem, cambium, and outer xylem (X 67). H, Trunk xylem transection (X 67). Nontranslocating phloem (fig. 35, F, G) is brown sapwood contrasts with the reddish- composed of stratified ares of thin-walled brown flattened fibers (20). Vessels are num- parenchyma and lignified thiclt-walled sclereids erous and small with thin walls. They are containing starch granules and crystals be- mostly solitary, but many occur as two or three tween wide rays. Parenchyma form arcs of radial and tangential cell groups. Vessels at the narrow tangential bands that form cells com- beginning of the growth ring tend to be slight- mon with the ray cells. Rays contain sclereids ly larger and more numerous than in the late at points not joining tangential parenchyma wood. Parenchyma are both paratracheal and bands. The translocating phloem (fig. 35G) apotracheal. Paratracheal parenchyma are consists of small dome-shaped groups of sieve sparse and restricted to occasional cells next to elements no thicker than about seven cells the vessels. Apotracheal parenchyma are beginning at the cambium. The groups of sieve abundant as cells either scattered or in short elements are separated by rays. one-cell bands that have no definite pattern. The xylem is diffuse-porous (fig. SbH). Fiber tracheids are moderately thick walled. Rings are clearly visible, and the thin, light Rays are 3- to 10-seriate. 92 PN-B5G4 FIGURE 36.—Parsley hawthorn {Crataegus marshallii Eggelst.). A, Leaf upper surface (X 120). B, Leaf lower surface (X 100). C, Leaf lamina transection (X 200). D, Leaf midrib transection (X 85). Rosaceae coarsely serrate, and the base cunéate or Parsley Hawthorn subcordate. The upper surface is dark green and undulat- (Crataegus marshallii Eggelst.) ing with fine wax striations over the ground Parsley hawthorn occurs in the Pineywoods epidermal cells (fig. 36A). Some long, twisted and Post Oak Savannah of Texas. It is a thorny nonglandular hairs are common. Glands, prob- shrub or small tree attaining a height of 6 m. ably hydathodes, occur at the tip of the teeth The crown is rounded and wide spreading. It of the leaf. mostly grows on sandy sites in woods, or hill- The lower surface (fig. 36ß) is slightly sides, in fence rows, and in open pastures. papillose and paler green. Numerous long, Leaf shape and surface twisted, unicellular nonglandular hairs are The leaves are 2 to 3.8 cm long by about 1.3 present, particularly on the veins. Stomata cm wide with five to seven deep lobes, alter- occur only on the lower surface ; they are slight- nate, simple, and deciduous ; the shape is ovate ly raised above the ground epidermal cells and to deltoid ovate, the apex acute, the margin are ranunculaceous. 93 PN-5565 FIGURE 36.—Parsley hawthorn (Crataegus marshallii Eggelst.)—Continued. E, Trunk periderm and outer phloem transection (X 175). F, Trunk phloem, cambium, and outer xylem (X 175). G, Trunk xylem transection (X 175). Leaf transection In the midrib (fig. 360), the xylem is cres- cent shaped with successive tiers of phloem and The lamina (fig. 36C) has a thin cuticle on fibers underneath. A few rhombic crystals are both epidermises. Inner walls of most epidermal cells on both surfaces are mucilaginous. Pali- present in the parenchyma at the edge of the fibers. Upper surfaces of both veins and midrib sade parenchyma are short and one to three cells deep ; spongy parenchyma are loosely are elevated above the plane of the interveinal tissue, giving rise to the undulating appearance packed. The larger vascular bundles are verti- cally transcurrent and contain fibers. Smaller of the leaf. vascular bundles occur entirely among the Stem transection spongy parenchyma. Vascular bundles are sur- rounded by a sheath of cells. A few clustered The outer bark is gray to brown, scaling off crystals are present in the bundle sheath. in large thin plates to expose reddish-brown 94 inner bärk. A phellogen arises in the inner non- translocating phloem and produces both phellem and phelloderm. Both the phellem and phello- derm cells are elongated tangentially. The plates peel off near the phellogen (fig. SGE), leaving a thin remnant of phellem for a protec- tive covering (183). Nontranslocating phloem is comprised of parenchyma and sclereids. The parenchyma are large and elongated tangen- tially; many are tanniferoua and contain small rhombic crystals. Sclereids form discontinuous tangential bands three to five cells wide, and many contain large rhombic crystals. The translocating phloem consists of sieve elements in one to three strata, two or three cells deep (fig. 36F). Parenchyma, as tangential one-cell lines, separate the strata of sieve elements. The xylem is diffuse-porous (fig. 36G). Ves- sels are small and thin walled, and almost all are solitary. Early and late wood vessels are about the same size. Parenchyma occur almost entirely as scattered, solitary cells. Most are apotracheal, but a few are associated with the vessels. Fibers are thick walled. Rays are one- to three-seriate. Black Cherry (Prunus serótina Ehrh.) Black cherry occurs in the Pineywoods, Gulf Prairies and Marshes, Post Oak Savannah, and Blackland Prairies of Texas. It usually grows to a tree 15 to 18 m tall with a trunk 6 to 9 dm in diameter with a narrow, oblong crown. It grows best on rich, moist lowland sites. Leaf shape and surface The leaves are 5 to 15 cm long by 2.5 to 4.6 cm wide, alternate, simple, and deciduous; the shape is narrowly oval to oblong-lanceolate, the apex acuminate, the margin finely serrate with incurved teeth, and the base cunéate. The upper surface is lustrous and dark green with slightly undulating waxy striations (fig. 37A). The leaf teeth are tipped with glands or hydathodes. The lower surface is lighter green than the upper surface and is slightly papillose (fig. B7B). Ranunculaceous stomata occur only on the lower surface. No trichomes were found on the upper surface and most of the lower sur- face area. Numerous reddish-brown, long, PN-55ee twisted hairs were present, but only along the FIGURE 37.—Black cherry (Prunus serótina Ehrh.). A, Leaf upper surface ( X 550). B, Leaf lower basal one-third to one-half of the midrib (fig. surface (X 550). C, Leaf lower surface midrib SIC). (X 26). 95 PN-B567 FIGURE 37. Black cherry (Prunus serótina Ehrh.)—Continued. D, Leaf lamina transection (X 208). E, Leaf midrib transection (X 99). F, Trunk periderm and outer phloem transection (X 85). G, Trunk phloem, cambium, and xylem transection (X 85). H, Trunk xylem transection (X 85). 96 Leaf transection was fragile and pulled away from the adjoining The lamina (fig. 37Z)) has a thin cuticle on rays during preparation. both surfaces. Epidermal cells vary in size. The The xylem is diffuse-porous (fig. SIH). Ves- palisade parenchyma are one cell deep; the sels throughout the growth ring are numerous, spongy parenchyma are loosely packed. Veins small, and about the same size. Vessels are have a prominent bundle sheath, and most have either solitary, or in small groups, or in radial fibers on the lower side. rows (64). An almost continuous tier of vessels The midrib (fig. S7E) has a crescent-shaped is produced at the beginning of early wood xylem. Underneath the xylem are successive growth. Parenchyma are sparse and scattered. arcs of phloem and fiber tiers, respectively. A Fiber tracheids are thin to thick walled. Rays few parenchyma contain either rhombic or are one- to six-seriate with most being three- to clustered crystals. four-seriate. Stem transection Macartney Rose (Rosa hracteata Wendl.) The outer bark is a rhytidome, reddish brown to nearly black, and exfoliating in small, per- Macartney rose grows in the Pineywoods, sistent, platy scales with upturned edges. The Gulf Prairies and Marshes, Post Oak Savan- phellogens arise deep in the secondary phloem nah, Blackland Prairies, Cross Timbers and and produce numerous layers of dark-staining, Prairies, and Edwards Plateau of Texas. It is elongated phellem and about 3 to 10 broadly an evergreen shrub, half climbing or trailing rectangular cells of phelloderm (fig. 37F). The and forming dense, impenetrable thickets to outer nontranslocating phloem consists mostly 6 m tall. It grows mostly in open fields on both of dark-staining parenchyma and numerous upland and lowland sites. clusters of large sclereids, some with large Leaf shape and surface rhombic crystals. Translocating phloem (fig. BIG) consists of a thin tier of sieve elements The leaves are 5 to 10 cm long, alternate, two to six cells deep adjacent to the cambium. odd-pinnately compound with 5 to 11 leaflets To the outside are several strata of crushed (mostly 7), and persistent. Leaflets are sieve elements and parenchyma. Ray paren- leathery ; the shape is oblong, elliptic, or chyma are tanniferous. The translocating tissue obovate, the apex acute to obtuse, the margin PN-6568 FIGURE 38.—Macartney rose {Rosa hracteata Wendl.). A, Leaf upper surface (X 600). B, Leaf overall lower surface (X 200). 97 PN-5569 FIGURE 38.—Macartney rose {Rosa bracteata Wendl.)^Continued. C, Leaf lower surface showing trichome and stomata (X 600). D, Leaf lower surface with marginal gland (X 220). E, Leaf lamina transeetion (X 235). crenate-dentate, and the base wedge shaped or occurs on both surfaces. Upper epidermal cells rounded. are mucilaginous and are much larger than the The upper surface is lustrous and dark green. lower ones. Most of the lamina interior is made It is slightly papillose with fine wax protru- up of three or four layers of elongated palisade sions (fig. 38A). The lower surface (fig. 385) parenchyma. Spongy parenchyma are moder- is paler and also somewhat papillose. Long, ately well packed, particularly next to the lower thin hairs are common, particularly on the epidermis. Vascular bundles lie among the veins. Stomata occur only on the lower surface. spongy parenchyma. They are surrounded by a Figure 38C shows a further enlargement of bundle sheath, and the larger ones contain the lower surface with a vein, base of a hair, fibers. and ranunculaceous stomata embedded in the In the midrib (fig. 38F), the xylem is cres- waxy surface. The leaf teeth are tipped with cent shaped. A tier of phloem is beneath the glands (fig. BSD). xylem. A few fibers lie in a discontinuous line outside the phloem. A few rhombic crystals are Leaf transeetion present in the parenchyma immediately below In the lamina (fig. BSE), a thin cuticle the vascular bundle. 98 '•^-^ - ^ «-'«•:*' " >}> >., j.*^'^ ^^-1^ -^-.:■-- -" - * 1 Í«J* ■■ liai Él ^ *• *• '-^ j- - ¡1 PN-557() FIGURE 38.—Macartney rose (Rosa bracteata Wendl.)—Continued. F, Leaf midrib transection (X 180). G, Stem periderm and outer phloem transection (X 85). H, Stem phloem, cambium, and outer xylem transection (X 85). /, Stem xylem transection (X 85). Stem transection The tissue containing sieve elements also seems The outer surface is reddish brown to gray to include cells that ultimately become fibers. and smooth except for the recurved thorns. It The xylem is diffuse-porous (fig. 38/). Ves- is formed by a thin periderm (fig. 38G). sels are small, but early wood vessels are slight- Underneath are corticallike parenchyma. The ly larger than those in the late wood. Most nontranslocating phloem is composed of suc- vessels are solitary with only a few in pairs. cessive strata of fibers and parenchym.a be- Parenchyma are scanty and scattered, occur- tween the rays (fig. 38, G, H). Translocating ring both next to the vessels and among the phloem (fig. 38//) consists of about three tiers fibers. Fibers are thick walled. Rays are 1- to of sieve elements three to six cells deep sepa- 15-seriate. Two to five uniseriate rays lie rated by strata of dark-staining parenchyma. between 4- to 15-seriate rays. 99 PN-5B71 FIGURE 39.—Guajillo {Acacia berlandieri Benth.). A, Leaflet upper surface (X 200). B, Leaflet lower surface (X 200). C, Leaflet lower margin (X 100). D, Leaflet midrib and lamina transaction 100 u'-: >: PN-5572 FIGURE 39.—Guajillo (Acacia berlandieri Benth.)—Continued. E, Trunk periderm and outer phloem transection ÍX 85). F, Trunk phloem, cambium, and outer xylem transection (X 85). G, Trunk xylem transection (X 85). 101 stem transection thin to medium thick walled and usually The outer bark is gray with shallow fissures gelatinous. Rays are mostly two-seriate. separating broad, flat ridges. It is comprised of a superficial periderm having about 10 Huisache [Acacia famesiana (L.) Willd.] layers of phellem (fig. B9E). Beneath the peri- Huisache grows in the Gulf Coast Prairies derm are two tiers of dark-staining paren- and Marshes, Post Oak Savannah, Blackland chyma separated by a continuous tier of Prairies, South Texas Plains, and Edwards sclereids. Nontranslocating phloem is composed Plateau. It is thorny and either a shrub with of alternate discontinuous tiers of fibers sepa- many stems flaring from the base or a tree up rated by dark-staining parenchyma (fig. 39, E, to 9 m tall with a stem to 4.6 dm in diameter. F). Translocating phloem (fig. 397^) consists It may have either a flat or a rounded crown. of a tier 6 to 10 sieve elements wide separated Huisache grows usually on deep loam or clay by tiers of fibers. soils. The xylem is ring-porous (fig. 39G), and most growth rings are thin. Early wood vessels Leaf shape and surface are medium sized, occurring either singly or in The leaves are 2.5 to 10 cm, long, alternate, small groups up to four cells. They grade bipinnately compound with two to eight pairs abruptly into small cells in the late wood. Late of rachises, and deciduous. The leaflets are 10 wood vessels are small and thick walled. They to 25 pairs on a rachis and are 2 to 6 mm long occur singly occasionally, but most are ar- by 1 mm wide; the shape is linear-oblong, the ranged either in radial files or in nests of apex acute or obtuse, the margin entire, and sometimes more than 20 cells. Parenchyma are the base inequilateral. abundant in tangential bands surrounding both Both the upper and lower surfaces are bright the early wood and late wood vessels. Apo- green. They are papillose with scaly wax de- tracheal parenchyma also lie in more or less posits (fig. 40, A, B, C). Rubiaceous stomata alternating strata with fibers. The fibers are are present on both surfaces (132). They are PN-5573 FIGURE 40.—Huisache [Acacia famesiana (L.) Willd.]. A, Leaflet upper surface (X 154). B, Leaflet upper surface (X 384). C, Leaflet lower surface {X 154). 102 difficult to see even in figure 40Z? because of of cells and underlain by an irregularly shaped the wax deposits. A few long, pointed hairs tier of sclereids with rhombic crystals. Non- were found on both surfaces of some leaves. translocating phloem (fig. 40, E, F) is made up of discontinuous strata of fibers and paren- Leaflet transection chyma, three to five cells wide. The translocat- The leaflets have a thin cuticle on both sur- ing phloem area (fig. 40F) is composed of tiers faces (fig. 4:00). Epidermal cells on both sur- of sieve elements plus parenchyma separated by faces are papillose, and some are mucilaginous. strata of fibers. The palisade parenchyma are one or two cells The xylem is ring-porous (fig. 40G). Early deep. Spongy parenchyma are moderately well wood vessels are medium sized, occurring packed except underneath the stomata, and singly or in multiples of two to five cells. The sometimes they are elongated similar to the early wood vessels are two or three groups deep palisade parenchyma. Veins lie in the middle of and may be interspersed by groups of much the leaflet. Both the veins and midrib have a smaller vessels. The transition between early bundle sheath. The midrib is round with about and late wood vessels may be either gradual or four layers of xylem and three layers of abrupt. Late wood vessels are small and thick phloem. A few rhombic crystals occur with the walled (fig. 40F). A few are solitary, but most veins and midrib. are either nested in groups or are arranged in Stem transection radial files frequently with 10 or more cells. Parenchyma are abundant, being mostly para- The outer bark is reddish brown with shal- low furrows separating scaly ridges. It is com- tracheal either as broad bands or as wide rings prised of a superficial phellogen that produces encompassing the vessels. Some parenchyma numerous layers of both phellem and phello- are present in the ring margins. Fibers are derm (fig. 40E). Phellem cells are thin walled thick walled and gelatinous. Rays are mostly and rectangular. Underneath is a tier of dark- two- to four-seriate, but some are up to six- staining phelloderm consisting of 5 to 10 layers seriate. PN-5574 FIGURE 40.—Huisache [Acacia farnesiana (L.) Willd.]—Continued. D, Leaflet midrib and lamina transection (X 322). E, Trunk periderm and outer phloem transection (X 85). 103 PN-5575 FIGURE 40.—Huisache \_Acacia famesiana (L.) Willd.]—Continued. F, Trunk phloem, cambium, and outer xylem transection (X 85). G, Trunk xylem transection Blackbrush Acacia are almost smooth, both with rubiaceous sto- (Acacia rigidula Benth.) mata. No trichomes were found on either surface. Blackbrush acacia grows in the Gulf Prairies and Marshes, South Texas Plains, Edwards Leaflet transection Plateau, and Trans-Pecos Mountains and Both leaflet lamina surfaces have a thick Basins. It is an erect, rigid, thorny shrub with cuticle (fig. 41C). The epidermal cells are tan- many stems from the base, attaining a height niferous. Palisade parenchyma are one or two of 4.5 m. It grows in open pastures, mostly on cells deep, and the spongy parenchyma are heavy soils, often forming impenetrable tightly packed. Usually spongy parenchyma are thickets. upright but are shorter than paHsade paren- chyma. Veins are round, sheathed by paren- Leaf shape and surface chyma, and located in the spongy parenchyma. Leaves are 1 to 2.5 cm long, alternate, bipin- The larger veins contain fibers. Rhombic crys- nately compound with one to two pairs of tals are present in the bundle sheath. rachises, and deciduous. The leaflets are two to The midrib (fig. 41Í)) is similar to the four pairs (rarely five) and 6 to 15 mm long lamina with the exception that the vascular by 4 to 8 mm wide ; the shape is elliptic to ob- bundle is larger. The vascular bundle is de- long, the apex rounded or mucronate, the lineated by a sheath of large, colorless paren- margin entire, and the base inequilateral. chyma cells, many of which contain rhombic Both surfaces are dark green. The upper crystals. Vascular tissue is surrounded by a (fig. 41A) and the lower (fig. AlB) surfaces tier of fibers two or three cells deep. 104 PN-5576FN-5576 FIGURE 41.—Blackbrush acacia {Acacia rigidula Benth.). A, Leaflet upper surface (X 500). B, Leaflet lower surface (X 500). C, Leaflet lamina midrib transection (X 428). D, Leaflet midrib transection (X 428). Stem transection uous strata of fibers and parenchyma (fig. 41, The outer bark is light to dark gray and E, F). Translocating phloem (fig. 41F) con- smooth. It is formed from shallow phellogens sists of a tier of about 5 to 10 sieve elements that produce 5 to 15 layers of phellem (fig. interspersed with fiber tiers. 41£'). Underneath are two thick tiers of dark- The xylem is ring-porous (fig. 41G). Early staining parenchyma separated by a continuous wood vessels are medium sized, thick walled, tier of sclereids, many with rhombic crystals. and occurring either singly or in groups up to Nontranslocating phloem contains discontin- 12 cells. They grade gradually to smaller late 105 PN-5577 FIGURE 41.—Blackbrush acacia (Acacia rigidida Benth.)—Continued. E, Stem periderm and phloem transection (X 85), F, Stem phloem, cambium, and outer xylem transection (X 85). G, Stem xylem transection (X 85). 106 wood vessels that also occur either singly or in long by 1.3 to 2.5 cm wide; the shape is oblong- small groups, usually in radial files. Paren- lanceolate to elliptical, the apex acute or chyma are abundant. Most are paratracheal in rounded, the margin crenulate, and the base wide rings around the vessels ; often they form acute or inequilateral. bands connecting the early wood vessels. The The upper surface is lustrous and dark green. rings around the late wood vessels usually do It is papillose with a scattering of long, pointed not coalesce. However, a few parenchyma are nonglandular hairs particularly along the mid- apotracheal, being diffuse among the fibers. rib and margin (fig. 42A). The lower surface Fibers are thick walled and gelatinous. Num- is yellow green and is slightly papillose with erous rhombic crystals are associated with the prominent veins. Although not shown in the fibers. The rays are mostly three- or four- photo (fig. 42ß), a moderate number of long, seriate; some are as many as six-seriate. pointed hairs were present on the midrib, whereas fewer were found on the lamina. Honeylocust (Gleditsia triacanthos L.) Stomata are present only on the lower surface Honeylocust grows in all areas of Texas but and are ranunculaceous. the Rolling Plains, High Plains, and Trans- Leaflet transection Pecos Mountains and Basins. It is a medium- sized tree usually 15 to 23 m hig-h with a trunk On the lamina (fig. 42C) a visible cuticle 6 to 9 dm in diameter. The crown is open and occurs on both surfaces. The cells of the epi- spreading with the trunk and branches usually dermis are slightly papillose. Palisade paren- armed with clusters of straight and branched chyma are one or two cells deep, and the thorns. It grows best in open areas on rich, spongy parenchyma are loosely packed. Veins moist sites, but it will grow on drier, upland are located primarily in the spongy paren- sites. chyma and have a sheath of parenchyma. The larger veins have fibers below the vascular Leaf shape and surface bundle. The leaves are 15 to 30 cm long, alternate, The midrib (fig. 42D) has a crescent-shaped both pinnately and bipinnately compound, and xylem and phloem. Thick-walled cells, either deciduous. The bipinnate leaves have four to collenchyma or fibers, lie both above the xylem seven pairs of rachises. There are 10 to 30 and below the phloem. A few rhombic and leaflets on the petiole or rachises, 2 to 5 cm clustered crystals are present in the perimeter PN-5578 FIGURE 42.^Honeylocust (Gleditsia triacanthos L.). A, Leaflet upper surface (X 200). B, Leaflet lower surface (X 230). 107 PN-5579 FIGURE 42.—Honeylocust {Gleditsia triacanthos L.)—Continued. C, Leaflet lamina transaction (X 218). D, Leaf- let midrib transection (X 175). E, Trunk periderm and outer phloem transection (X 85). of vascular bundles of both the midrib and several phellogens in the secondary phloem veins. that produce a thick phellem tier (fig. Í2E). Stem transection Nontranslocating phloem (fig. 42, E, F) con- sists mostly of parenchyma and large clusters The outer bark is grayish brown to black with deep, narrow fissures separating scaly of sclereids ; however, a few fibers are present. ridges often with clusters of branched thorns. Numerous rhombic crystals are associated with The thorns arise from axillary meristems (15). the sclereids. Translocating phloem (fig. 42/^) The outer bark is a rhytidome consisting of is a tier of sieve elements 10 to 15 cells deep. 108 PN-5580 FIGURE 42.—Honeylocust {Gleditsia triacanthos L.)-—Continued. F, Trunk phloem, cambium, and outer xylem transection (X 85). G, Trunk xylem transection (X 85). The sieve elements are interspersed with Texas except the Pineywoods. It is a thorny parenchyma. shrub or tree up to 15 m tall with crooked, The xylem (fig. 42, F, G) is ring-porous drooping branches and a rounded crown {68). with a band of large vessels two to four cells It grows in open areas on sandy to clayey sites wide. Most of the vessels are solitary, but some and competes best in areas receiving 15 to 30 occur in groups of two or three. Some early inches of rainfall during the year. The growth wood vessels have gum deposits. Transition pattern and morphology of honey mesquite has from early to late wood vessels is gradual. Late been summarized by Meyer et al. {100) and wood vessels are small and generally in groups Haas et al. {59). An annotated bibliography up to about 20 cells. Paratracheal and marginal of literature on mesquite has been edited by parenchyma are abundant. Paratracheal paren- Schuster {131). chyma encircle the vessels and usually form an Leaf shape and surface irregular band in the early wood. Parenchyma also surround the medium-sized late wood ves- The leaves are 10 to 25 cm long, alternate, sels. Late in the growing season, the paren- bipinnately .compound of 2 (rarely 3 or 4) chyma usually form wavy, tangential bands rachises with 6 to 15 pairs of leaflets each, around the smallest vessels. Marginal paren- and deciduous. Leaflets are 1.8 to 6 cm long by chyma are abundant but form a discontinuous about 6 mm wide; the shape is linear, the line. Fibers are thick walled. Rays are 1- to apex acute or obtuse, the margin entire, and 14-seriate, with most being 6- to 9-seriate. the base cunéate or rounded. Wendt et al. {172) found that a log-log relationship exists Honey Mesquite between the sum of the lengths of the rachises [Prosopis juliflora (Swartz) DC. var. and the total surface area of the leaf. Both surfaces are dark green. glandulosa (Torr.) Cockerell] The upper surface is papillose with a recog- Honey mesquite, also known as Prosopis nizable midrib. Leaves from greenhouse plants glandulosa Torr. {30), grows in all areas of have a fine pebbly appearance because of a thin 109 PN-5581 FIGURE 43.—Honey mesquite IProsopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell] (all samples ex- cept A were from plants in the field). A, Greenhouse plant leaflet upper surface (X 200). B, Leaflet upper surface (X 200). C, Leaflet lower surface (X 200). D, Leaflet lamina transection (X 174). cuticle (fig. 43A). The mature leaf from a tree leaves, and none were present on the leaves in the field has a more crusty appearing upper scanned. cuticle (fig. 435). Rubiaceous stomata are present and are more numerous on the lamina Leaflet transection than on the midrib. The cuticle of the lower The lamina (fig. 43/)) has thick cuticle on surface of a mature leaf from the field is also both surfaces {106). Palisade parenchyma are rough (fig. 43C). The stomata are slightly less usually three cells deep, and spongy paren- numerous than on the upper surface. Few sto- chyma are tightly packed. Elongated, dark- mata occur on the midrib. Only a few one-celled staining tanniferous cells are present, as well nonglandular hair.s have becT) found on the as thin-walled secretory cells in the mesophyll. 110 PN-5582 FIGURE 43.—Honey mesquite iProsopis juUflora (Swartz) DC. var. glandulosa (Torr.) Cockerell]^—Continued. E, Leaflet midrib transaction (X 174). F, Trunk periderm transection (X 85). G, Trunk phloem, cambium, and outer xylem transection {X 85). H, Trunk xylem transection (X 85). Ill Veins are round with a peripheral circle of are sometimes confluent around the late wood large, thin-walled bundle sheath cells. Even out vessels. A few parenchyma are apotracheal dif- near the margin of the leaflet the veins contain fuse among the fibers. Several growth-regulat- fibers under the vascular bundle. ing herbicides reduce the size of the vessels The midrib (fig. 43£') has a circular xylem and inhibit cell-wall thickening of parenchyma underlain by a crescent-shaped tier of phloem. {98, 12Jf.). The fibers are thick walled and Large gelatinous fibers lie at the sides and usually gelatinous. Rays are one- to five-seriate, below the vascular bundle. A layer of large but most are three- or four-seriate. thin-walled cells forms the bundle sheath. A few rhombic crystals are associated with the Mescalbean bundle sheath of both the midrib and veins. [Sophora secundiflora (Ortega) Lag.] Stem transection Mescalbean occurs in Gulf Coast Prairies and Marshes, Blackland Prairies, South Texas The outer bark is reddish brown, thick, fur- Plains, Edwards Plateau, and Trans-Pecos rowed, and scaly (68). It is a rhytidome made Mountains and Basins of Texas. It is an ever- up of phellogens that form deep in the second- green shrub or rarely a small tree up to 11 m ary phloem (fig. 4BF). Phellogens produce only high with a trunk 1.5 to 2 dm in diameter. three to six cells of phellem and a couple cells The crown is narrow with numerous upright of phelloderm usually. Nontranslocating phloem branches. It grows in open pastures both on (fig. 43, F, G) consists of alternating, almost moist sites and upland limestone soils. continuous tiers of fibers and phloem. Trans- locating phloem (fig. 43G) is a tier adjacent to Leaf shape and surface the cambium containing sieve elements, paren- The leaves are 10 to 15 cm long, alternate, chyma, and in this instance, three tiers of odd-pinnately compound, and persistent. The fibers. leaflets are 5 to 13 (usually 5 to 9), 2.5 to 6 The xylem is ring-porous (fig. 43H). Early cm. long by 1.3 to 4 cm wide, and leathery; the wood vessels are large and either solitary or in shape is elliptic-oblong or oval, the apex groups of two to five. They usually grade grad- rounded, notched, or mucronate, the margin ually into small cells in the late wood. Late entire, and the base gradually narrowed. wood vessels occur singly or in groups up to 10 The upper surface is lustrous and dark green. cells. Parenchyma are abundant, mostly para- It is only slightly undulating (fig. 44A). No tracheal, forming a band surrounding the ves- trichomes were present on the upper surface. sels in the early wood and wide bands, which The lower surface (fig. 44B) is sHghtly lighter PN-B583 FIGURE 44.—Mescalbean [Sophora secundiflora (Ortega) Lag.]. A, Leaflet upper surface (X 500). B, Leaflet lower surface (X 550). 112 green than the upper surface and is also slight- both above and below the vascular tissues. ly undulating. Only a few long, pointed hairs Rhombic crystals are abundant around the were present near the base of the midrib. Sto- periphery of both veins and the midrib. mata occur only on the lower surface and seem Stem transection to be ranunculaceous ; a raised extension of the cuticle on the guard cells forms a rim partially The outer bark is dark gray to black, broken covering the pore. into shallow fissures separating flattened ridges. It is a rhytidome composed of several Leaflet transection phellogens deep in the secondary phloem that Both leaflet surfaces of the lamina have a produce 6 to 10 layers of phellem (fig. 44Í7). thick cuticle making these tissues difficult to Nontranslocating phloem consists of abundant cut and keep intact (fig. 44C). The upper epi- parenchyma with numerous, discontinuous tiers dermal cells are slightly larger than the lower of fibers (fig. 44£'). The translocating phloem ones. Palisade parenchyma are two or three region (fig. 44^") consists of three reproducing cells deep, and spongy parenchyma are mod- multiples of sieve elements, parenchyma, and erately tightly packed. Veins lie in the meso- fiber tiers. The sieve elements, parenchyma, phyll parenchyma and are oblong shaped with and fiber tiers are about three, three, and five fibers both above and below the vascular cells wide, respectively. Rays widen progres- bundle. sively from the cambium to the outer phloem. The midrib (fig. 44D) has crescent-shaped The xylem is ring-porous (fig. 44G). Vessels tiers of xylem and phloem. Tiers of fibers occur are small both in the early and late wood (33), PN-B584 FIGURE 44.—Mesoalbean ¡Sophova secumliflora (Ortega) Lag.]—Continued. C, Leaflet lamina transection (X 178). ß, Leaflet midrib transection (X 180). 113 PN-5B85 FIGURE 44.—Mescalbean [Sophora secundiflora (Ortega) Lag.]—Continued. E, Trunk periderm transection (X 85). F, Trunk phloem, cambium, and outer xylem transection (X 85). G, Trunk xylem tran- section (X 85). The vessels at the ring form almost a contin- around the vessels. Apotracheal parenchyma uous tier 1 to 10 cells wide. Late wood vessels form scattered bands between vessels and sev- form radial or oblique bands. Parenchyma are eral marginal layers along the growth ring. both paratracheal and apotracheal. Paratra- Fibers are thick wahed and about G66 urn long cheal parenchyma occur in moderate numbers (33), Rays are two- or three-seriate. 114 PN-5586 FIGURE 45.—Creosotebush [Larrea tridentata (DC.) Coville]. A, Leaflet upper surface (X 220). B, Leaflet lower surface (X 210). C, Leaflet lamina transection (X 85). Zygophyllaceae Leaf shape and surface The leaves are about 1 cm long, opposite, Creosotebush bifoliate compound, and persistent. The two [Larrea tridentata (DC.) Coville] leaflets are 5 to 10 mm long by about 2 mm Creosotebush grows in the South Texas wide, opposite, curved, leathery, with an odor Plains, Edwards Plateau, and Trans-Pecos of creosote ; the shape is ovate to oblong, the Mountains and Basins. It is an evergreen, apex acute, the margin entire, and the base of two leaflets joined. Smaller leaves are pro- aromatic shrub attaining a height of 3.4 m duced under moist rather than under dry con- with numerous stems radiating upward from ditions. Occasionally the leaves are cleaved into the ground line. Creosotebush has no well- three to five sections (126). Seedlings from defined trunk. The plant is a widespread desert California are more erect and have a more shrub growing mostly on the alluvial plains, open growth form with more slender and less particularly shallow, gravelly soils over caliche incurved leaflets than seedlings from, south- (27). Life-history characteristics have been eastern Arizona, New Mexico, and Texas described (106, 170). (181). 115 The leaflet surfaces are dark green to yellow- ish green. Both the upper surface (fig. 45A) and the lower surface (fig. 45ß) are papillose. There are numerous long, flat, pointed hairs that lie on the surface. About the same number of ranunculaceous stomata occur on both surfaces. Leaflet transection On the lamina (fig. 45C) there is a thin cuticle on both surfaces. Numerous epidermal cells on both surfaces contain dark-staining materials, which are probably resins and tannin that are important for imparting the char- acteristic creosote odor (78). The leaflet is generally isobilateral in that the palisade pa- renchyma are two or three cells deep inside both the upper and lower epidermis (126), but the parenchyma inside the lower surface are slightly shorter than the upper tier of paren- chyma. The walls of the epidermal cells are much thicker than the mesophyll parenchyma (126). Spongy parenchyma are located cen- trally. Barbour et al. (12) found pahsade pa- renchyma only beneath the upper epidermis with spongy parenchyma extending to the lower epidermis in a South American collection. Veins lie in the spongy parenchyma and are round. A sheath of large parenchyma sur- rounds the vascular bundles. Clustered crystals are common in the parenchyma particularly next to the veins. The midrib (fig. 45ZJ) has a circular vascu- lar strand. The xylem is ovate, whereas in the phloem it is crescent shaped. Fibers almost completely encircle the vascular tissue. Stem transection The outer bark is dark gray to black with the older branches roughened by small scales. Periderm may be composed simply of phellem produced from phellogens arising near the sur- face (fig. AhE). Sometimes the phellogens originate deep in the phloem to form a rhyti- dome. Underneath the rhytidome is a thick tier consisting of parenchyma and large numbers of sclereids. Many sclereids, particularly near the surface, are several times longer tangen- PN-5587 tially than thick. Numerous rhombic crystals FIGURE 45.—Creosotebush [Lar7-ea tridentata (DC.) Coville]—Continued. D, Leaflet midrib transection are present among the parenchyma and scle- (X 85). E, Stem periderm transection (X 175). reids. The outer nontranslocating phloem tissue contains mostly flattened parenchyma 116 PN-5588 FIGURE 45.- -Creosotebush [Larrea tridentata (DC.) Coville]—Continued. F, Stem phloem, cambium, and outer xylem (X 77). G, Stem xylem transection (X 77). and discontinuous bands of fibers plus scle- grows in open rangeland on shallow sites and reids. Translocating phloem (fig. 45F) consists in canyons in west Texas. of at least two tiers of sieve elements plus parenchyma separated by a tier of fibers plus Leaf shape and surface sclereids. The leaves are 1.3 to 3.6 cm long, opposite or The xylem is semiring-porous (fig. 45G). crowded in fascicles at nodes, pinnately com- Vessels are small and scattered with a tendency pound, and persistent. The leaflets arc four to to form, a continuous band at the growth ring. eight pairs, 5 to 15 mm long by 2 mm wide, The vessels are almost entirely solitary with leathery, folded at night and sometimes during thick walls, and only a few are paired. Paren- the heat of the day; the shape is hnear to chyma are almost entirely apotracheal as dif- oblong, the apex acute, the margin entire, and fuse cells and as one-cell-wide tangential bands. the base oblique. The fibers are thick walled. Rays are mostly Both surfaces are lustrous dark green. Both two-seriate, rarely one- or three-seriate. the upper surface (fig. 46A) and the lower surface (fig. 46S) have a general undulating Guayacan surface with papillose epidermal cells. Stomata are abundant on both surfaces ; they are ranun- [Porlieria angustifolia (Engelm.) Gray] culaceous and have cuticle extensions of the guard cells, partially covering the pores (fig. Guayacan grows in the Gulf Prairies and 46C). No trichomes were found. Marshes, Cross Timbers and Prairies, South Texas Plains, Edwards Plateau, and Trans- Leaflet transection Pecos Mountains and Basins. It is an evergreen The lamina (fig. 46D) has a moderately shrub or tree to 6.5 m tall with a stem 2.5 dm thick cuticle on both surfaces. The leaflet meso- in diameter. The trunk is well defined, thick phyll cells are tightly packed and seem to be stubby, and stiff with compact branches. It entirely alike rather than being divided into 117 PN-5589 FIGURE 46.—Guayacan [Porlieria angustifolia (Engelm.) Gray]. A, Leaflet upper surface (X 210). B, Leaflet, lower surface {X 205). C, Leaflet lower surface stomata (X 520). D, Leaflet lamina transection (X 338). palisade and spongy parenchyma. Veins are a superficial phellogen that produces a tier of central and round. phellem about eight cells wide at the surface The midrib (fig. 46È') contains a round (fig. 46^"). Beneath the periderm are two fibrovascular strand. The xylem is more or less layers of brown-staining parenchyma separated scattered in the lower part of a bundle of fibers. by a tier of sclereids. Outer, nontranslocating Phloem is crescent shaped below the xylem. phloem (fig. 46, F, G) has alternating dis- Also, a tier of fibers one to three cells deep continuous strata of fibers and parenchyma. lies beneath the phloem. A few cells both near The translocating phloem region (fig. 46G) the midrib and lamina have clustered crystals. contains two or three tiers of sieve elements plus parenchyma separated by a tier of fibers. Stem transection Cells in some rays enlarge from near the The outer bark is gray to black and broken cambium outward. into rough scales. The periderm is formed from The xylem is more or less diffuse-porous 118 PN-5590 FIGURE 46.—Guayacan [Porlieria angustifolia (Engelm. ) Gray]—Continued. E, Leaflet midrib transection (X 208). F, Trunk periderm and outer phloem (X 85). G, Trunk phloem, cambium, and outer xylem (X 85), H, Trunk xylem transection (X 85). 119 (fig. 46, G, H). The vessels are small and thick of 2.5 dm. The crown is either rounded or walled. Many vessels are solitary, and others spreading. It grows mostly on shallow, dry are arranged in groups or radial files of two soils. to eight vessels. Parenchyma are abundant in more or less confluent bands around the vessels Leaf shape and surface and in the growth ring margins. The fibers are The leaves are 8 to 10 cm long, alternate, odd- thick walled, and some are mucilaginous. Rays pinnately compound with 5 to 13 leaflets are one- to four-seriate. (usually 7 to 9) on a broadly winged rachis, leathery, and persistent. The leaflets are 8 to Rutaceae 32 mm long, opposite, except for the terminal Colima (Lime Pricklyash) leaflet ; the shape is ovate to obovate, the apex [Zanthoxylum fagara (L.) Sarg,] rounded or notched, the margin bluntly crenu- late-toothed, and the base wedge shaped or Colima, or lime pricklyash, grows in the Gulf rounded. Prairies and Marshes and the South Texas The upper leaflet surface is bright green, Plains. It is an aromatic, thorny evergreen shiny, and smooth except for the fine striations shrub or tree to 9 m tall with a trunk diameter of the cuticle (fig. 47A). Secretory glands oc- PN-5591 FIGURE 47.—Colima (lime pricklyash) [Zanthoxylum fagara (L.) Sarg.]. A, Leaflet upper surface (X 540). B, Leaflet marginal gland on upper surface (X 140). C, Leaflet lower surface (X 540). 120 cur on the margin of the leaflets and at the The outer layers have partially collapsed, but teeth of the winged petiole (fig. 47ß). The low- most of the outer phloem tissue is parenchyma er surface is somewhat lighter green than the with a scattering of small groups of sclereids. upper surface. It is more or less papillose with The translocating phloem is about eight cells cuticle striations covering the ground epidermal deep. cells (fig. 47C). Stomata occur only on the low- The xylem is diffuse-porous (fig. 47G). Ves- er surface. They appear to be ranunculaceous. sels are very small with thick walls and are An extension of the guard cells forms a lip that about the same size throughout the ring. They partially covers the pore. No trichomes were are either solitary or in groups of two or three found on either surface of the leaf. cells. Parenchyma are mostly diffuse. Fibers Leaflet transaction are medium thick walled. Rays are one- to two-seriate. The leaflet lamina (fig. 47Z)) has a promi- nent cuticle on both surfaces. The upper epi- Anacardiaceae dermal cells are large and thin walled, and they were difficult to keep intact while microtom- Shining Sumac (Rhus copallina L.) ing. Palisade parenchyma are one or two cells deep, and the spongy parenchyma are loosely Shining, flameleaf, or wing-rib sumac, grows packed. Veins are round and lie in the meso- in all areas of Texas except the Rolling Plains, phyll. Secretory cavities are present in the High Plains, and Trans-Pecos Mountains and boundary between the palisade and spongy par- Basins. It is a slender-branched shrub or small tree up to 8 m tall. It grows on a wide variety enchyma. The midrib (fig. 47-E') has an ovate xylem. Underneath is a crescent-shaped tier of of sites from open rocky hillsides to shaded, phloem. A one- to two-cell tier of fibers lies moist bottom lands. below the phloem. Leaf shape and surface Stem transection The leaves are 13 to 30 cm long, alternate; The outer bark is gray, aromatic, thin, and the rachis is broadly winged, odd-pinnately either smooth or with warty excrescences. It compound, and deciduous. The leaflets are 7 to arises from a superficial phellogen that pro- 17, 2.5 to 9 cm long by 1.3 to 3.3 cm wide, and duces three to six layers of phellem (fig. 47F). opposite except for the terminal leaflet; the Mr' PN-5592 FIGURE 47.—Colima (lime pricklyash) [Zanthoxylum fagara (L.) Sarg.]—Continued. D, Leaflet lamina tran- section (X 20S).E, Leaflet midrib transection (X 208). 121 PN-5593 FIGURE 47.—Colima (lime pricklyasli) [Zanthoxylum fagara (L,) Sarg.]—Continued. F, Trunk periderm, phloem, and cambium transection (X 85). G, Trunk xylem transection (X 85). PN-559^ FIGURE 48.—Shining sumac (Rkus copalKna h.). A, Leaflet upper surface (X 220). B, Leaflet lower surface (X 220). 122 shape is ovate to lanceolate, the apex acute or cell hairs (fig. 48A). The lower surface is a acuminate, the margin entire or few-toothed, slightly lighter, dull green than the upper sur- and the base inequilateral and rounded to face. It is slightly papillose with a moderate cunéate. number of both short hairs and long hairs (fig. The leaflet upper surface is lustrous green. 48ß). More hairs occur on the midrib and large It is papillose with a scattering of short one- veins than on the lamina. Ranunculaceous PN-5595 FIGURE 48.—Shining sumac (Rhus copallina L.)—Continued. C, Leaflet lamina transection (X 330). D, Leaflet midrib transectioii {X 85). E, Trunk periderm transection {X 85). 123 PN-5596 FIGURE 48.—Shining sumac (Rhus copallina L.)—Continued. F, Trunk phloem, cambium, and outer xylem tran- section (X 85). G, Trunk xylem transection (X 85). stomata occur only on the lower side. Either Stem transection some dirt or loose wax lies on the surface. The outer bark is greenish brown, thick, and Leaflet transection with thin scales. It is composed of many phel- lem cells arising from superficial phellogens The lamina (fig. 48C) has a thick cuticle on (fig. 48£'). The nontranslocating phloem is both surfaces, but the upper one is slightly made up of parenchyma and resin ducts. No thicker than the lower one. The upper epider- fibers or sclereids were found in the phloem. mal cells are large and flat. Lower epidermal Some parenchyma contain tannin ; others con- cells are smaller and more rounded. Palisade tain clustered crystals. Many parenchyma lie in parenchyma are one cell deep and long; spongy tangential rows. The resin ducts lie more or less parenchyma are loosely packed. The small vas- in tangential rows, are oval, and have one or cular bundle lies mostly in the spongy paren- two layers of cells around them similar to Rhus chyma and has a sheath of cells larger than in glabra L. (52). the vascular tissue. The xylem is ring-porous (fig. 48, F, G). In the midrib (fig. 4SD), the vascular sys- Early wood vessels are medium sized, occuring tem is a series of collateral bundles with resin two to four cells deep. They grade gradually ducts in the phloem. The lower five bundles smaller progressively deeper into the late wood. form a more or less crescent-shaped tier. The Late wood vessels are small. Sometimes they upper surface of the midrib is ridged with the are solitary, but most lie in small clusters. Par- tip containing a group of medium thick-walled enchyma are sparse and not easily identified. cells. A few clustered crystals are present in Some seem to be paratracheal, and others occur the parenchyma below the vascular tissue. in marginal bands three to five cells wide prob- 124 PN-5597 FIGURE 49.—Poison ivy {Rhus radicans L.). A, Leaflet upper surface (X 240). B, Leaflet lower surface (X 240). C, Leaflet lower surface trichomes (X 550). ably with septate fibers. The fibers are medium stream bottoms, hillside woods, or in fence thick walled, and many have gelatinous thick- rows. enings. Rays are one- to three-seriate. Leaf shape and surface Poison Ivy (Rhus radicans L.) The leaves are alternate, trifoliate (rarely Poison ivy, also known as Rhus toxicoden- five-foliate) compound, and deciduous. The ter- dron L., grows in all areas of Texas except the minal leaflet is 3.3 to 20 cm long by 1.3 to 13 High Plains. It is a poisonous, either suberect cm broad. The lateral leaflets are 3.3 to 17 cm shrub or woody-stemmed vine. The stem may long by 1.3 to 10 cm wide. The leaflet shape is be glabrous to densely pubescent and may have oval to lanceolate, the apex acute to acuminate, aerial roots. As a vine, it may grow to the top the margin entire, dentate or three to seven- of tall trees. Poison ivy grows on many sites lobed, and the base wedge shaped to rounded. but is usually found in shaded areas either in The upper leaflet surface is dull green. The 125 .- ~- Í, -^ Vî-T:^>-V_./ '.^'^í ,-^,'' '.-"^■"w^,.» ît ^ .*;;' PN-B59S FIGURE 49.—Poison ivy {Rhiis radicans L.)—Continued. D, Leaflet lamina transection (X 410). E, Leaflet midrib transection (X 102). F, Trunk periderm and outer phloem transection (X 85). surface of the ground epidermal cells is level hairs. Also, there are a few multicelled, club- with fine striations of cuticle (fig. 49A). Veins shaped glandular hairs (fig. 49C). A moderate are prominent, and there is a sparse scattering number occur on the lamina ; many are on the of unicellular hairs. midrib and large veins. The lower surface is paler green than the upper surface. The surface over the ground Leaflet transection epidermal cells is sHghtly wrinkled with fine The lamina (fig. 49D) has only a thin cuti- cuticle striations (fig. 49, B, C). Stomata oc- cur only on the lower surface and appear to be cle on both surfaces. Palisade parenchyma are ranunculaceous. Edges of the guard cells extend one cell deep, and spongy parenchyma are outward, partially covering the pore. Numerous loosely packed. Veins are round, lie in the trichomes are present. Most are long one-cell mesophyll, and usually have a resin duct. The 126 PN-559H FIGURE 49.—Poison ivy {Rhus radicans L.)—Continued. G, Phloem and cambium transection (X 85). H, Trunk xylem transection (X 85). vascular bundle is surrounded by a sheath of The xylem is ring-porous (fig. 49iï). Early parenchyma. wood vessels are medium to large with thick The midrib (fig. 49Ê') IK rectangular shaped walls and are one to four cells deep. They de- with a ridge filled with medium thick-walled crease abruptly in size in the late wood. Late cells on the upper surface. Vascular tissue is wood vessels are either solitary or in small comprised of a more or less ring of collateral radial groups. Parenchyma are scarce but al- bundles surrounded by a tier of fibers. The most entirely paratracheal. Fibers are medium phloem lies outside the group of vessels in each thick walled. Rays are one- to four-seriate. bundle and contains a resin duct. Stem transection Cyrillaceae The outer bark is brown with thin ridges and Sw^amp Cyrilla (Cyrilla racemiflora L.) may contain trichomes and aerial roots. It is Swamp cyrilla grows only in the Pineywoods comprised of 10 to 15 layers of phellem and and Gulf Prairies and Marshes of Texas. It is 2 to 5 layers of phelloderm produced from a a shrub or small tree to 9 m tall with a short superficial phellogen (fig. 49F). The outer, trunk and spreading irregular branches. It nontranslocating phloem is composed of paren- grows mostly in shaded, swampy areas, but chyma, and oval-shaped resin ducts (fig. 49, also occurs on sandy ridges adjacent to water F, G). Most rays enlarge tangentially, progres- courses (67). sively further from the cambium toward the periderm. Translocating phloem (fig. 49G) has Leaf shape and surface only three to six layers of large sieve elements The leaves are 5 to 10 cm long by 8 to 25 outside the cambium. mm wide, alternate, simple, persistent, and 127 PN-5600 FIGURE 50.—Swamp cyrilla {Cyrilla racemiflora L.). A, Leaf upper surface (X 230). B, Leaf lower surface (X 230). C, Leaf lamina transection (X 195). leathery ; the shape is oblong-obovate to elliptic, ly three cells) deep, and spongy parenchyma the apex acute or obtuse, the margin entire, and are loosely packed. Most veins contain fibers the base wedge shaped. both above and below the vascular bundle and The upper surface is lustrous dark green. It are vertically transcurrent. is smooth with rather well-defined veins (fig. The vascular system in the midrib is a com- 50A). The lower surface is paler green and is plex structure (fig. 50Z)) comprised of a de- only slightly papillose (fig. 50ß). Stomata oc- pressed, oval bundle with an accessory strand cur only on the lower surface and are ranun- on top. The entire vascular system is sur- culaceous. The guard cells have ridges of cuticle rounded by a sheath of fibers one to four cells that partially cover the pores. A fungal hypha deep. A few parenchyma near the veins and is present; in a fall sampling, fungi had cov- midrib contain clustered crystals. ered about half of the leaf surface, presumably Stem transection favored by the warm, moist conditions. No trichomes were found. The outer bark is gray or reddish brown, spongy, and with small, shreddy scales. It is Leaf transection composed of several superficial phellogens that The lamina (fig. 50C) has a thin cuticle on produce long, thin-walled phellem to the out- both surfaces. Epidermal cells are slightly flat- side (fig. SOE"). Two or three cell layers in the tened. Palisade parenchyma are two cells (rare- phellogen region are thick walled, similar to 128 (■''. ^.>'^r;\. -"^^''f/'O^^^ ^ PN-5601 FIGURE 50.—Swamp cyrüla (Cyrilla racemiflora L.)—Continued. D, Leaf midrib transection (X 48). E, Trunk periderm and outer phloem transection (X 85). F, Trunk phloem, cambium, and outer xylem transection (X 85). G, Trunk xylem transection (X 85). sclereids. Usually one or two layers of dark- are three to five cells wide at the cambium and staining phelloderm are present. The fragile flare widely toward the outside of the stem phellem cells make the bark spongy to the touch. (fig. 50, £", F). The outer phloem (fig. 50, E, F) contains par- The xylem (fig. 50G) is diffuse-porous (67). enchyma that become flattened, dark staining, Vessels are very small, thin walled, mostly and thick walled. The translocating phloem lies solitary; the others appear largely as more or next to the cambium where sieve elements are less tangential pairs caused by the overlapping interspersed with parenchyma (fig. 60F). Rays ends. Vessels in the spring wood are slightly 129 larger than in the late wood. Perforation plates vannah areas of Texas. It is an evergreen tree are scalariform, averaging 30 to 40 bars (125). growing to 12 to 18 m tall with a trunk 3 to Parenchyma are sparse, as cells diffuse among 6 dm in diameter with short, crooked branches, the fibers and along the vessels (67). Fiber and a narrow to rounded crown. It usually tracheids are medium thick walled with the grows in shaded, deep, moist bottom lands. late wood cell walls thicker than in the spring It is used widely in uplands, however, as an wood. The rays are three- to six-seriate. ornamental. Aquifoliaceae Leaf shape and surface American Holly (Ilex opaca Ait.) The leaves are 5 to 10 cm long by 2.5 to 3.8 cm wide, alternate, simple, and persistent for American holly grows in the Pineywoods, 3 years ; the shape is elliptical to oblong, the Gulf Prairies and Marshes, and Post Oak Sa- apex acute or spinose, the margin entire to PN-5602 FIGURE 51.—American holly {Ilex opaca Ait.). A, Leaf upper surface (X 200). B, Leaf lower surface (X 200). C, Leaf lamina transection (X 172). 130 PN-5603 FIGURE 51.—American holly (Ilex opaca Ait.)—Continued. D, Leaf midrib transection (X 85). E, Trunk periderm and outer phloem transection {X 85). f. Trunk phloem, cambium, and outer xylem transection (X 85). G, Trunk xylem transection (X 85). 131 spinose-dentate, and the base wedge shaped or hlF) consists of a tier of sieve elements 3 to 10 rounded. Development of new leaves has been cells deep and interspersed with parenchyma. discussed by Milbocker and Craig {108). The xylem is diffuse-porous (fig. 51G). Ves- The upper leaf surface is lustrous dark green sels are numerous and very small; most are to yellowish green. Heavily shaded leaves are polygonal. They are either solitary or in more the darkest green (165), The upper surface is or less radial strings that sometimes cross ring almost smooth except for fine striations of the boundaries. Parenchyma are primarily apotra- cuticle (fig. 51A). Although not seen in the cheal and diffuse among the fiber tracheids; photographs, a few unicellular hairs were pres- paratracheal parenchyma are scanty. Fiber ent. The lower surface is light green or yellow. tracheids are moderately thick walled (6Í), The cuticular striations are more pronounced Most rays are three- to six-seriate; a few are than on the upper surface (fig. 51S). Veins uniseriate. are prominent. Stomata are ranunculaceous, present only on the lower surface, and sur- Yaupon {Ilex vomitoria Ait.) rounded by a rampart of cuticle (87). Yaupon occurs in the Pineywoods, Gulf Prairies and Marshes, Post Oak Savannah, and Leaf transection South Texas Plains of Texas. It is evergreen, The leaf lamina has a thick cuticle (7 to 10 either as a thicket-forming shrub with many ¡im) (151) on both surfaces and often extends stems from the base, or a small tree growing to part way or completely to the base of the epi- 8 m tall with a trunk diameter to 3 dm,. The dermal cells (fig. 51C). The upper epidermal crown is dense and rounded. It usually grows cells are mucilaginous. Palisade parenchyma as an understory, reaching its largest size in are three cells deep, and spongy parenchyma low, moist woods, but it is common on upland are loosely packed. Clustered crystals are com- claypan soils. mon among the palisade parenchyma. Vascular Leaf shape and surface bundles in the veins are round with a bundle sheath of thin-walled cells. Fibers are abundant The leaves are 4 to 6 cm long by 2 to 3 below the vascular tissue in the vein. cm wide, alternate, simple, and persistent; the shape is elliptic to oblong, the apex obtuse or In the midrib (fig. 51D), there is a one-cell rounded, the margin crenate, and the base hair on the upper surface. Both the upper and obtuse or rounded. The leaves are thick and lower epidermal tiers are two cells deep across leathery. the midrib but only one cell deep in the lamina The upper surface is lustrous dark green, region. The vascular bundle is an elongated, and the lower surface is paler. Both the upper slightly crescent-shaped cylinder (73), Vascu- surface (fig. 52A) and the lower surface (fig. lar tissue is composed of a cylinder of xylem 525) are smooth except for wavy striations of surrounded by a cylinder of phloem,. Paren- cuticle. Stomata occur only on the lower sur- chyma are present in the center of the cylinder face; they are ranunculaceous and are sur- with one-cell-wide rays extending through the rounded by a rampart of cuticle. Also, cuticle xylem into the phloem (10), A ring of fibers extensions of the guard cells partially cover the surrounds the phloem. pores. No trichomes were found on either sur- Stem transection face. Glands were present on the tips of the teeth. The outer bark is light or dark green, thin, and either smooth or roughened by small pro- Leaf transection tuberances. It arises from superficial phello- The lamina has a thick cuticle on both sur- gens that produce 10 to 15 layers of phellem faces (fig. 52C). The upper epidermal cells are (fig. blE), Occasionally phelloderm occurs up larger than the lower cells. Some of the upper to five cells deep (183), Outer, nontranslocat- epidermal cells are mucilaginous. Palisade cells ing phloem consists of parenchyma with large are two or three deep and are only slightly groups of sclereids, some with rhombic crystals elongated. Spongy parenchyma are loosely (fig. 51, E, F), Translocating phloem (fig. packed. The veins are round in the mesophyll 132 PN-5604 FIGURE 52.—Yaupon {Ilex vomitoria Ait.). A, Leaf upper surface (X 580). B, Leaf lower surface (X 580). C, Leaf lamina transection (X 243). and have a sheath of parenchyma. Most of the Stem transection larger veins have fibers. The outer bark is brownish to mottled gray The midrib (fii?. 52Z)) has a round vascular or almost black, thin, and smooth except for strand. The xylem is oval. Phloem almost com- thin, small scales. It is composed of phellem pletely encircles the xylem, and a tier of fibers cells produced by superficial phellogens (fig. one to three cells deep lies at the bottom and 52E). Underneath are parenchyma and large up along most of both sides outside the phloem. groups of sclereids. Sometimes the outermost Ashworth (10) found that the vascular bundle sclereids form an almost continuous ring, but may be either a cylinder or an arc on the same of these cells most form isolated clusters among plant. the parenchyma. The translocating phloem con- 133 tains parenchyma among the sieve elements are medium thick walled. Some rays are three- (fig. 52F). to nine-seriate; others are uniseriate. The xylem is diffuse-porous (fig. 52G). Ves- sels are small and are either solitary or ar- Aceraceae ranged in radial strings. Some lines of vessels Boxelder {Acer negundo L.) cross the growth ring. Parenchyma are apotra- cheal and moderately abundant. Most are dif- Boxelder grows in the Pineywoods, Gulf fuse among the fiber tracheids. Fiber tracheids Prairies and Marshes, Post Oak Savannah, PN-B605 FIGURE 52.—Yaupon (Ilex vomitoria Ait.)—Continued. D, Leaf midrib transection (X 180). E, Trunk periderm transection (X 85). F, Trunk phloem, cambium, and outer xylem transection (X 85). G, Trunk xylem transection (X 85). 134 Blackland Prairies, Cross Timbers and Prairies, surface is paler. Both the upper surface (fig. and South Texas Plains of Texas. It commonly 53A) and the lower surface (fig. 53, B, C) are is a tree growing to 23 m with a trunk 6 to 9 papillose and have long, pointed unicellular dm in diameter, forming a broad, rounded hairs, particularly on the veins (1Î7). The up- crown. Boxelder grows on a wide variety of per lamina has only a few hairs. The lower sites but makes its best growth in shaded, moist lamina surface usually has a moderate number areas (65). of hairs. The midrib and large veins have many Leaf shape and surface hairs. Stomata are ranunculaceous and are con- fined to the lower surface. A cuticular lip on The leaves are 15 to 38 cm long, opposite, the guard cells partially covers the pore (fig. odd-pinnately compound with three to seven 53C). (sometimes nine) leaflets, and deciduous. The leaflets are 5 to 10 cm long by 4 to 8 cm wide; Leaflet transection the shape is ovate to lanceolate, the apex acumi- A thin cuticle occurs on both surfaces of the nate, the margin irregularly serrate or lobed, lamina (fig. 53Z>). The upper epidermal cells and the base wedge shaped, rounded, or cordate. are larger than the lower ones. The mesophyll The upper surface is light green; the lower parenchyma are usually four cells deep with no PN-B606 FIGURE 53.—Boxelder {Acer negundo L.). A, Leaflet upper surface {X 220). B, Leaflet lower surface (X 220). C, Leaflet lower stomata (X 1,200). D, Leaflet lamina transection (X 338). 135 clear demarcation between palisade and spongy is flat. The lower one is crescent shaped. In the tiers. The vein is vertically transcurrent with middle is a small medullary bundle. The vas- some fibers above and below the vascular bun- cular strand is almost entirely encircled with dle; a secretory sac appears to be present in fibers. Numerous parenchyma in both the the phloem. Large rhombic crystals are com- lamina and midrib contain clustered crystals. mon in the mesophyll, and most lie immediately under and perpendicular to the upper midrib. Stem transection The midrib has a ridge on the upper surface The outer bark is light to dark gray or gray (fig. 53Í7). Vascular tissue is comprised of brown, thin, and with rounded ridges separated three superimposed bundles. The upper bundle by shallow fissures. Phellogens arise deep in PN-5G07 FIGURE 53.—Boxelder (Acer negundo L.)—Continued. B, Leaflet midrib transection (X 77). F, Trunk periderm and outer phloem transection (X 85). G, Trunk phloem, cambium, and outer xylem transection {X 85). H, Trunk xylem transection (X 85). 136 the nontranslocating phloem to form a rhyti- llJf, IH). Vessels are moderately small and dome (fig. 53F). The outer phellem cells are occur either singly or in radial files of two to thin walled ; the inner three or four layers are five cells. Parenchyma are fairly sparse. Most thick walled and form a continuous band. Non- parenchyma are present as a tier of four to translocating phloem is comprised of paren- seven cells deep along the ring margins. How- chyma and groups of sclereids and fibers. ever, some parenchyma form partial or com- Toward the outside, the sclereid plus fiber plete one-cell rings around the vessels. Fiber groups form several more or less continuous tracheids are medium thick walled. Rays are tiers. Toward the inside of the phloem, the one- to five-seriate. sclereid groups are mostly scattered among the parenchyma. Some rhombic crystals are asso- Red Maple {Acer rubrum L.) ciated with the parenchyma and sclereids. The Red maple grows in the Pineywoods and Gulf translocating phloem (fig. 53G) is composed of Prairies and Marshes of Texas. It is a tree at- a tier of large sieve elements 3 to 10 cells deep taining a height of 30 m with a trunk diameter outside the cambium. New phloem is produced of 9 dm. The crown is irregular to rounded. about a month earlier in the spring than the The roots are shallow and wide spreading. Red new xylem {166). maple usually grows in shaded sites in swamps, The xylem is diffuse-porous (fig. 53//) {65, along streams, or in alluvial woods, but it oc- PN-seos FIGURE 54.—Red maple {Acer rnhrum L.). ^, Leaf upper surface (X 550). B, Leaf lower surf ace (X 550). C, Leaf lamina transaction {X 223). 137 casionally grows on upland sites, particularly The xylem is diffuse-porous (fig. 54G) as an ornamental. (14i). Vessels are moderately small and are either solitary or in radial groups of two to Leaf shape and surface four cells. Parenchyma are sparse either par- The leaves are 5 to 15 cm in diameter, op- tially (occasionally completely) surrounding posite, simple, and deciduous; the shape is or- the vessels or forming a tier about three cells bicular, usually with three (sometimes five) deep on the growth ring margin. Fiber tra- palmate lobes. The lobes are short and broad; cheids are moderately thick walled. Rays are the apex is acuminate, the margin coarsely one- to five-seriate (105). serrate, and the base broadly wedge shaped, rounded, or subcordate. Sugar Maple (Acer saccharum Marsh.) The upper surface is bright green. It is al- most smooth except for fine striations of cuticle Sugar maple grows in the Pineywoods of (fig. 54A). The lower surface is pale green and Texas. It is a tree reaching 30 m and a trunk often waxy. It is papillose with prominent veins diameter of 8 dm. It has a dense, broad, round- (fig. 54J5). Ranunculaceous stomata occur only ed crown. Sugar maple makes the best growth on the lower surface and appear as slits in the in shaded, rich, moist, well-drained soils. epidermal cells. No trichomes were found on Leaf shape and surface the upper surface, but a few long, pointed hairs were present on the lower large veins, espe- The leaves are 8 to 13 cm in diameter, op- cially where they joined together. posite, simple, and deciduous; the shape is or- bicular, usually palmately five-lobed (rarely Leaf transection three-lobed). The lobe apex is acuminate and The lamina (fig. 54C) has little cuticle. Up- the margin is entire or sparingly wavy toothed. per epidermal cells are larger than the lower The leaf base is broadly cunéate, rounded, or ones. Palisade parenchyma are one cell deep. subcordate. Leaf shape varies somewhat from Both the palisade and spongy parenchyma one area to another and from tree to tree (7, are loosely packed. The veins are vertically 38). transcurrent. The upper leaf surface is bright green. The The midrib has a small ridge on the upper surface is slightly papillose, and the veins are surface (fig. 54D). The vascular strand is com- prominent (fig. 55A). The lower surface is prised of three tiers. The uppermost bundle is paler green than the upper surface and is long and slightly crescent shaped. The lowest glaucous (fig. 55ß). Ground epidermal cells tier is U-shaped and composed of several bun- are slightly papillose. A moderate number of dles. The middle tier is a small medullary long, pointed hairs occur on the lamina and bundle. A few clustered crystals are present in particularly on the veins. Ranunculaceous sto- the parenchyma, particularly near the vascular mata occur only on the lower surface. The ones bundles. on this leaf were covered with wax. Stem transection Leaf transection The outer bark is dark gray, deeply furrowed, The lamina (fig. 55C) has a thin cuticle on and scaly. It is a rhytidome consisting of deep both surfaces. Upper epidermal cells are larger phellogens producing numerous layers of phel- than the lower ones. Palisade parenchyma are lem in the nontranslocating phloem (fig. ME). one cell deep, and the spongy parenchyma are The outer, nontranslocating phloem is composed loosely packed. Veins are vertically transcur- of more or less alternate tiers of parenchyma rent. A few rhombic crystals are associated and fiber plus sclereids. A few rhombic crystals with the veins. are present among the parenchyma and scle- In the midrib the vascular strand is varia- reids. Translocating sieve elements are large ble. In figure 55D, the vascular system is es- (fig. 54F) and 6 to 10 cells deep. Almost con- sentially a round series of vascular bundles. In tinuous strata of fibers plus parenchyma occur another leaf the vascular strand was more or among the sieve elements. less in three tiers similar to red maple. A ring 138 PN-Gß09 FIGURE 54.^Red maple (Acer riibrum L.)—Continued. D, Leaf midrib transection (X 85). E, Trunk periderm transection {X 85). F, Trunk phloem, cambium, and outer xylem transection {X 93). G, Trunk xylem tran- section (X 85). 139 PN-5610 FIGURE 55.—Sugar maple {Acer saccharum Marsh.). A, Leaf upper surface (X 210). B, Leaf lower surface (X 200). C, Leaf lamina transection (X 360). of fibers one to four cells deep encircles the ferous phelloderm cells two to eight layers deep vascular tissue. are produced. Occasionally some of the outer phloem is cut off by the phellogens. Nontrans- Stem transection locating phloem contains abundant numbers of The outer bark is dark gray, thick, and with sclereids intermingled with some fibers mostly deep furrows separating long, irregular, scaly in more or less tangential tiers with paren- plates {6Jt). It is a rhytidome consisting of chyma (fig. 55F). The translocating phloem numerous superficial phellogens that produce consists of a tier of sieve elements three to six three to five layers of thin-walled phellem cells cells deep (50). that alternate with three to five layers of thick- The xylem is diffuse-porous (fig. 55G). Ves- walled cells (fig. 55Ê^). Chang {25) indicates sels are either solitary or in radial multiples of that the alternating layers of thin-walled and two to four cells (rarely to seven). Parenchy- thick-walled cells are often continuous over 50 ma are sparse, Hmited to a few cells around times, depending on the age of the bark. Inside the vessels and to about a three-cell tier at the the last phellogen, parenchymatous and tanni- margin of the growth ring. Fiber tracheids are 140 '^-'' >■ t ''jfK\ %^ \: ■^1.' '" / ' '. St' ■? ;^-- "' " ^- .' ''; .ri * ■ * ■ ■ -- -^ '^: À ^ f\:. ^ ; V - -■/-'>." ., " ' •B •^ o .-'>:/.-/ 11 ■- ,. ^U. I -C^ - '" 4 ,j „ , * <-•• '/;>:% ; V : . /\ • ' , ■"»,-0 ^; - ■ ■ . * ■, > ;"' «■ tsTo-'.\ \ :-i <''£;■ ' Í PN-G611 FIGURE 55.—Sugar maple (Acer saccharum Marsh.)—Continued. D, Leaf midrib transection (X 85). E, Trunk periderm transection (X 85). F, Trunk phloem, cambium, and outer xylem transection (X 85). G, Trunk xylem transection (X 85). 141 PN-B612 FIGURE 56.—Texas colubrina \_Coîubrina texensis (Torr. & Gray) Gray]. A, Leaf upper surface (X 220). B, Leaf lower surface (X 220). C, Leaf lower surface stomata (X 1,100). D, Leaf lamina transection {X 440). moderately thick walled. Rays are one- to eight- vate, or elliptic, the apex rounded, the margin seriate, with most being either one- or four- to minutely toothed with glands, and the base six-seriate {14-i). wedge shaped, rounded, truncate, or subcordate. The upper leaf surface is grayish green ; the Rhamnaceae lower surface is lighter green. Both the upper Texas Colubrina surface (fig. 56A) and the lower surface (fig. [Colubrina texensis (Torr. & Gray) Gray] 56B) are slightly papillose and have numerous long, pointed multicelled hairs, particularly on Texas colubrina grows in the Gulf Prairies the veins. Stomata occur only on the lower sur- and Marshes, Cross Timbers and Prairies, face and are ranunculaceous (fig. 56C). The South Texas Plains, and Edwards Plateau of guard cells have small cuticular ridges that Texas. It is a thicket-forming shrub usually 1 partially cover the pore. to 2 m tall, rarely over 5 m tall, with spreading Leaf transection twigs. The plant grows largely on open, semi- arid prairie soils, particularly in rocky areas. The lamina (fig. 5QD) has only a thin cuticle on both surfaces. The upper epidermal cells are Leaf shape and surface much larger than the lower ones. Many upper The leaves are 1.3 to 2.5 cm long, alternate, ones are mucilaginous. Palisade parenchyma simple, and deciduous; the shape is ovate, obo- are one or two cells deep, and the spongy par- 142 PN-5G13 FIGURE 56.—Texas colubrina [Colubrina texensis (Torr. & Gray) Gray]—Continued. E, Leaf midrib transection (X 225). F, Stem periderm transection (X 87). G, Stem phloem, cambium, and outer xylem transection (X 85). H, Stem xylem transection (X 87). enchyma are loosely packed. Clustered crystals veins. In the midrib (fig. 66E), the xylem and occasionally are present in the parenchyma of phloem are crescent shaped. Many of the paren- the lamina. Most veins are vertically transcur- chyma are tanniferous. rent, but the smallest ones are embedded in the mesophyll. A sheath of large, usually tannifer- Stem transection ous, parenchyma cells surrounds the smaller The outer bark is gray and either smooth or 143 cracked into small, short scales. It arises from fibers are thick walled and usually gelatinous. superficial phellogens producing few to numer- Rays are one- to three-seriate and contain ous layers of phellem (fig. 56F). The outer, starch and som.e rhombic crystals. nontranslocating phloem is mostly parenchyma with many of the cells being tanniferous (fig. Lotebush Condalia 56, F, G). Only small isolated groups of fibers [Condalia obtusifolia (Hook.) Weberb.] or aclereids, usually fewer than 10, are present. The translocating phloem, (fig. 56G) is a tier Lotebush condalia, also known as Ziziphtis of sieve elements 6 to 10 cells deep and is ac- obtnsifolia (T.»feG.) Gray {30), grows in the companied by many parenchyma. Gulf Prairies and Marshes, Cross Timbers and Prairies, South Texas Plains, Edwards Plateau, The xylem is semiring-porous (fig. 5GH). Rolling Plains, and Trans-Pecos Mountains and Most rings are either thin or incomplete be- Basins of Texas. It is a stiff, spiny, much cause of the slow-growing nature of the plant. branched shrub growing to about 3 m tall. It Vessels are medium sized and are only slightly grows on a variety of semiarid, usually shallow larger in early wood than in late wood. A few sites on both limestone and neutral soils. are solitary, but most occur in groups of 2 to S (as many as 15) either in radial files or in Leaf shape and surface tangential tiers. Parenchyma are sparse, form- The leaves are 1.3 to 3.3 cm long, alternate, ing a one-cell layer around vessel groups. The simple, and deciduous ; the shape is elliptic. PN-5614 FIGURE 57.^Lotebush condalia [Condalia obtusifolia (Hook.) Weberb.]. A, Leaf upper surface (X 220). B, Leaf lower surface (X 220). C, Leaf lamina transection (X 223). 144 ovate, or narrowly oblong, the apex obtuse or are vertically ti'anscurrent, but most are em- acute, the margin entire to coarsely serrate, bedded in the mesophyll. Veins are surrounded and the base acute. The teeth are tipped with by a sheath of large tanniferous parenchyma. glands. A few of the parenchyma near the veins contain The upper surface is dark green and papil- clustered crystals. lose (fig. 57A). The lower surface is paler The midrib (fig. 57D) contains a crescent- green and is wavy, slightly papillose, and with shaped xylem and phloem. Numerous large prominent veins (fig. 57S). Stomata are ra- cells surrounding the vascular bundle contain nunculaceous and occur only on the lower sur- tannin. face of the leaf. Although not shown in the photographs, a few long, pointed hairs were Stem transection present on both surfaces, particularly near the The outer bark is light or dark gray and midrib. smooth. It originates from phellogens arising near the surface (fig. blE). The outer, non- Leaf transection translocating phloem contains mostly paren- The lamina (fig. 57C) has a thin cuticle on chyma with isolated groups of sclereids. both surfaces. The upper epidermal cells are Translocating phloem (fig. 57f) contains nu- generally larger than the lower ones, and a few merous layers of sieve elements interspersed of the upper ones are mucilaginous on the inner with parenchyma and groups of sclereids. half of the cell. The mesophyll has slightly Rhombic crystals accompany some of the elongated palisade-type cells under both sur- sclereids. faces and more or less spherical spongy par- The xylem is diffuse-porous (fig. 57G). The enchyma in the center. Some of the mesophyll vessels are medium to small in size and have cells are tanniferous. A few of the larger veins thick walls. They are either solitary or in radial PN-5615 FIGURE 57.—Lotebush condalia [Condalia obUisifolia (Hook.) Weberb.]—Continued. D, Leaf midrib transection (X 85). E, Stem periderm and outer phloem transection (X 93). 145 PN-GËIO FIGURE 57.—Lotebush condalia {Condalia ohttisifolia (Hook.) Weberb.]—Continued. F, Stem phloem, cambium, and outer xylem transection (X 85). G, Stem xylem transection {X 82). files of two to eig-ht cells. Parenchyma are liptic or oblong, the apex acute, obtuse, round- abundant. They are paratracheal around the ed, or mucronato, the margin entire, and the vessels and apotracheal as wavy one- to three- base rounded to acute. cell-wide bands joining the paratracheal par- The upper surface is lustrous dark green. enchyma. Also, marginal bands of parenchyma The ground epidermal cell surface is smooth of one to four cells occur at the growth ring. (fig. 58Ä). However, there is a scattering of Fibers are thick walled and gelatinous. Rays long, pointed hairs. The lower leaf surface is are one- to four-seriate. lighter green than the upper surface. The epi- dermal cells are highly papillose and waxy. The Coyotillo veins are conspicuous (fig. 58, B, C). No [Karwinskia humholtiana (R. & S.) Zuce] triehomes were found on the lower surface. Ra- Coyotillo occurs in the Gulf Prairies and nunculaceous stomata are present only on the Marshes, South Texas Plains, Edwards Plateau, lower surface and are inconspicuous (fig. 58C). and Trans-Pecos Mountains and Basins in Tex- Cuticular extensions partially cover the pore. Most leaves have black spots on both the upper as. It most generally occurs on dry plains and prairies of South Texas and near the mouths and lower laminar interveinal surfaces and black streaks on the lower veinal surface. of the Pecos and Rio Grande rivers. It is usu- ally a shrub 1 to 2 m tall but may grow to a Leaf transection height of 7 m. The lamina (fig. 58Z)) has a prominent cuti- Leaf shape and surface cle on the upper epidermis. The upper epi- Leaves are 2 to 4.5 cm long by L3 to 2 cm dermal cells are larger than the lower ones. wide, opposite, simple, deciduous, conspicuously Palisade parenchyma are one to three cells pinnate, and parallel veined; the shape is el- deep. Spongy parenchyma are loosely packed. 146 PN-5617 FIGURE 58.—Coyotillo IKarwinskia humboltiana {R. & S ,) Zuce.]. A, Leaf upper surface {X 200). B, Leaf lower surface {X 200). C, Leaf lower surface (X 500). D, Leaf lamina transection (X 349). Small lateral veins are vertically transcurrent. tanniferous cells. A couple of mucilage recep- Many large solitary crystals are present in en- tacles are in the lower left parenchyma of the larged palisade parenchyma. Some clustered midrib. These receptacles occur also in the crystals are present in the parenchyma, espe- larger veins. In some leaf sections these areas cially near the veins. stained black. In the midrib (fig. 5SE), the xylem is cres- cent shaped with a thick tier of phloem under- Stem transection neath. Outside the phloem is a thin tier of The outer bark is gray and smooth. The peri- 147 PN-5618 FIGURE 58.-—-Coyotillo [Karwinskia humboltiana (R. & S.) Zuce]—Continued. E, Leaf midrib transection 148 derm consists of superficial phellogens that Leaf shape and surface produce tiers of phellem about 10 cells deep The leaves are 13 to 15 cm long by 8 to 10 (fig-. 58F). The outer phloem is comprised cm wide, alternate, simple, and deciduous; the largely of parenchyma with long tiers of fibers shape is broadly ovate, the apex acute or acu- and sclereids two to four cells deep (fig. 58, minate, the margin coarsely serrate, and the F, G). Rhombic crystals are abundant among base commonly inequilateral and obliquely cor- the fibers and sclereids. There are numerous date or almost truncate. There is some varia- parenchyma among the translocating sieve ele- tion in taxonomic descriptions of the genus ments, and many contain tannin (fig. 58G). Tilia ; therefore only representative characters The xylem is diffuse- to semiring-porous from one tree are presented here. (fig. 5SH). The vessels are small and are either The upper surface is dark green. It is papil- solitary or in radial files up to four cells {121). lose with occasional long nonglandular hairs A slightly higher concentration of vessels oc- (fig. 59A). The lower surface is lighter green curs at the beginning of the early wood than than the upper surface. The leaf scanned had later on, but the vessels at various parts of the a sparse number both of long one-cell hairs, as growth ring are about the same size. Paren- shown on the upper surface, and stellate hairs chyma are sparse, occurring paratracheally on the lower surface, as shown in figure 59ß. partially around the vessels in a one-cell layer. Tufts containing numerous one-cell and stellate Fibers have medium thick walls and are usu- hairs occur at the junctions of the larger veins ally gelatinous. Rays are one- to three-seriate. on the lower surface of the leaf. Stomata are present only on the lower surface and are ra- Tiliaceae nunculaceous (fig. 59, B, C). The stomata are American Basswood {Tilia americana L.) of various sizes, and the guard cells have a raised lip of cuticle that partially covers the American basswood grows in the Pineywoods pore. of Texas. It grows to a tree usually 18 to 24 m tall with a trunk diameter of 6 to 9 dm. The Leaf transection crown is rounded and dense. It grows best on The lamina (fig. 59Z>) has little apparent shaded, moist bottom land. cuticle. The upper epidermal cells are larger PN-56I9 FIGURE 59.—American basswood {Tilia americana L.). A, Leaf upper surface (X 210). B, Leaf lower surface (X 210). 149 PN-5620 FIGURE 59.—American basswood {Tilia americana L.)—Continued. C, Leaf lower surface {X 550). D, Leaf lamina transection (X 393). E, Leaf midrib transaction (X 108). F, Trunk periderm and outer phloem transection (X 85). than the lower ones and generally either the the upper surface. The vascular strand consists entire or lower half are mucilaginous. Palisade of an almost completely closed ring of phloem parenchyma are one cell deep, and spongy par- and xylem surrounding a central medullary enchyma are loosely packed. The veins are bundle. A ring of fibers completely encircles vertically transcurrent, and some sheath cells the vascular strand. Several mucilage cells or contain rhombic crystals. About 11 cm of veins canals He in the parenchyma, particularly near occur per square cm of lamina (115). the lower epidermis. These cells are also present The midrib (fig. 59E) has a slight ridge on in the large veins. 150 PN-5621 FIGURE 59.^American basswood {Tilia americana L.)—Continued. G, Trunk phloem, cambium, and outer xylem transection (X 85). H, Trunk xylem transaction (X 85). Stem, transection The vessels are small and numerous with walls The outer bark is light brown to gray, thick, laminar in structure (31). They are either soli- and with deep furrows separating narrow, flat- tary or in radial or tangential groups of 2 to topped ridges. It is a rhytidome with phello- about 15 cells. Parenchyma are abundant both gens producing both tanniferous phellem and as tangential apotracheal short, one-cell bands phelloderm deep in the nontranslocating phloem and also as marginal bands one to four cells (fig. 59F). Ten or more flattened phellem cells wide at the growth ring. Fiber tracheids are are produced. Usually two to five almost thin walled. Rays are one- to seven-seriate; square phelloderm cell layers arise inside the most are one-, three-, or four-seriate (91). phellogen. The nontranslocating phloem con- sists of numerous strata of parenchyma two to Tamaricaceae four cells deep, fibers one or two cells deep, and remnants of sieve elements. Some compan- Saltcedar (Tamarix pentandra Pall.) ion cells associated with nontranslocating sieve Saltcedar occurs in the Rolling Plains and tubes become sclerified (4-8). Translocating Trans-Pecos Mountains and Basins of Texas. phloem consists of numerous strata of large French tamarisk {Tamarix gallica L.), a simi- sieve elements one or two cells deep among the lar species, occurs in all areas but the Piney- tiers of parenchyma and fibers (fig. 59G) woods. Post Oak Savannah, and Blackland (185). The sieve elements may translocate food Prairies of Texas. Both species have escaped materials for 1 to 5 years (47). Many paren- from cultivation. Saltcedar is either a shrub chyma are tanniferous. The ultrastructure of the secondary phloem has been described by with contorted branches or a tree with a Evert and Murmanis (51). Plastids have since twisted trunk growing to 9 m tall. The crown been found in sieve tubes and companion cells is wide spreading. Saltcedar is widely culti- of translocating tissue {4-9). vated for ornament, erosion control, and wind- The xylem is diffuse-porous (fig. 59iî) (64)- breaks. It prefers moist soils, growing on saline 151 PN-5622 FIGURE 60.—Saltcedar (Tamarix pentandra Pall.)- A, Terminal leaf surfaces {X 110). B, Older leaf surfaces (X 110). C, Older leaf surface {X 550). D, Terminal leaf transection (X 172). or alkaline sites along water courses in the The terminal leaves are whitish or bluish, drier areas of Texas. small, overlapping and sharp pointed, as shown partially embedded in the silver paint used to Leaf shape and surface affix the specimen to the scanning stub (fig. The leaves are overlapping and sealelike, 0.2 60A). Leaves on older twigs are overlapping to 3 mm long, alternate, and persistent; the and sleevelike (fig. 60, A, B). Both have a shape is deltoid to lanceolate, the apex acute papillose surface. The small tip leaves and the to acuminate, the margin entire, and the base ends of the sleevelike leaves have almost only sessile to stem. epidermal ground cells. The sides of the sleeve- 152 y-i X . .'■i ] -' /-^ ív- ;^ . ■ 1' . .^ «jí. PN-5623 FIGURE 60.—Saltcedar {Tamarix pentandra Pall.)^Continued. í/, Older leaf transection (X 166). f, Trunk peri- derm transeetion (X 87). like leaves (fig. 60, A, B, C) also show two compound organs consisting of eight cells com- levels of indentation. Each small, shallow in- posed of two inner, vacuolate, collecting cells dentation contains a ranunculaceous stoma. The and six outer, densely cytoplasmic, secretory long axis of the stomatal pore lies perpendicu- cells. The secretory cells are completely en- lar to the long axis of the leaf (138). Stomata closed by a cuticular layer except along part of were not found on the underside of the sleeve- the walls between the collecting cells and the like leaves. The deep indentations each contain inner secretory cells (21, 37, 158). Palisade a salt gland. No trichomes were found. parenchyma are present below the salt glands. The mesophyll consists of about three layers of Leaf transeetion elongated palisade parenchyma and two to five Figure GOD shows a transeetion through the layers of large, spherical spongy parenchyma. sleevelike leaf and small stem. A thin cuticle Also, several storage tracheids are present covers the epidermis of the leaf and increases among the parenchyma. Vascular bundles most- with age (173). The outer epidermal cells are ly lie in the spongy parenchyma and are devoid slightly larger than the inner ones, and some of fibers. of the outer ones divide horizontally (peri- clinially). Both stomata in the shallow indenta- Stem transeetion tions and salt glands in the deep crypts are The outer bark of the trunk is dark brown to shown on the outer epidermis. The upper sur- deep purple, thin, and with shallow fissures faces of the guard cells of the stomata are re- separating flat, elongated ridges. It is a rhyti- cessed, and are almost even with the base of dome comprised of phellogens arising deep in the epidermal cells (fig. QOE). Salt glands are the secondary phloem (fig. 60F). The non- 153 PN-5624 FIGURE 60.—Saltcedar {Tamarix pentandra Pall.)-—-Continued. G, Trunk phloem, cambium, and outer xylem tran- saction (X 87). H, Trunk xylem transaction (X 83). translocating- phloem (fig. 60, F, G) has large Savannah, and Blackland Prairies of Texas. It numbers of parenchyma, many containing is a thicket-forming cactus, usually a shrub 1.5 tannin. Also, convex tiers of fibers three to six to 6 dm tall, rarely to 20 dm. It usually grows cells deep connect the rays. Many sclereids on open, semiarid rangeland, particularly on form in the rays of the phloem. Rhombic crys- shallow, rocky soils. tals are common among the sclereids. The The leaves are 1.3 cm or less long, green, translocating phloem (fig. 60G) contains small awl shaped, and early deciduous (fig. 61A). sieve elements. This discussion deals primarily with young and The xylem is semiring-porous (fig. 60//). old stems. Vessels are medium to small. Early wood ves- sels occur in radial files of two to eight cells. Stem shape and surface In wide rings, more vessels, mostly solitary, The young stems are 2.5 to 33 cm long and form in the middle. The late wood vessels are 0.8 to 1.3 cm in diameter, ascending, cylindric, very small and in clusters. The transition from and spiny. They are either smooth or fluted early wood to late wood is gradual. Parenchyma (fig. 61A) with a spine and glochids forming are moderately abundant and are paratracheal, in the aréole above the leaves (fig. 61S). The forming a layer around the vessels or vessel surface is light to dark green. It it papillose groups. Fibers are medium thick walled. Rays with stomata (fig. 61C) (28). The stomata are are 6- to 12-seriate. rubiaceous (157), and the long axis of the guard cells lies parallel to the long axis of the Cactaceae stem. The old stems have a flaky, waxy surface Tasajillo Cactus with no stomata (fig. GID). Neither new nor old stem surfaces (other than aréoles) have (Opuntia leptocauUs DC.) trichomes. Tasajillo, or pencil cactus, occurs in all areas The aréole develops from meristematic tissue of Texas except the Pineywoods, Post Oak in the axil of the leaf (IS). Spines and glochids, 154 PN-5625 FIGURE 61.—Tasajillo cactus (Opuntia leptocmiUs DC). A, New stems with leaves (X 2). B, New stem aréole (X 27). C, New stem surface (X 210). D, Old woody stem surface (X 195). 155 V- V * ^ '•»' A 'V, ■/ t - '■'■.,' V >. í'^ ^^ < r_~ ;■ Í Í ^".1 IVIC N '\: ■ 1 ■ .A-- ■; n0 < A "^s; _V;' ■;■ ■: '; '^ '^- >, ■= '\ \ > E ■ÄÄ F '■■%. ; í ^ . ,a^ '/.. .^ PN-562G FIGURE 61.—Tasajillo cactus (Opuntia leptocaulis DC.)—Continued. E, New stem outer area transection (X 85). F, New stem inner area transection (X 85). G, Old woody stem periderm, phloem, cambium, and outer xylem transection (X 85). íí, Old woody xylem transection (X 85). 156 or short spines, form in the aréole (fig. 61S) are thick walled. Rays are mostly 6- to 10- (116). Spines and glochids both are scabrous seriate; the cells are mostly cuboidal. because of the projecting- lower ends of the sclerified surface cells (123, ISO). Spines are Lindheimer Pricklypear attached to the aréole by cork that is produced (Opuntia lindheimeri Engelm.) by a hypodermal phellogen (IS). The glochid is more easily detached from the plant than the Pricklypear grows in all areas of Texas; spine because it connects to the aréole with an however, Lindheimer pricklypear does not unsclerified zone of parenchyma (55, 123). At occur in the Cross Timbers and Prairies, Roll- the base of the aréole are long, pointed multi- ing Plains, or High Plains. It is a heavy-bodied, celled hairs developing from epidermal cells. thicket-forming cactus attaining a height of 1 See also characters of Lindheimer pricklypear, to 4 m. It may grow either erect or more or another Opuntia species (fig. 62). less prostrate. The leaves (fig. 62A) are early deciduous, so primarily the stem characteristics Stem transection will be described. A moderately thick cuticle (about 4 /i.m) Stem shape and surface covers the epidermal cells on the young stem (fig. QIE) (28). Beneath the epidermis is a The stems, joints or pads, are 15 to 28 cm layer of hypodermis in which many of the cells long, 13 to 25 cm broad, and about 1.3 cm thick, contain large clustered crystals (28, 179). succulent, set with leaves and aréoles 2.5 to 5.8 Below is a tier of about five rows of radially cm apart that contain tufts of barbed glochids flattened, thick-walled collenchyma cells with less than 0.5 cm long, one to six (usually one conspicuous intercellular pitting. The hypoderm or two) erect or semierect spines 2 to 6 cm and collenchyma tiers are continuous except long, and long multicelled hairs (fig. 62, A, B). for long, tubular cavities beneath the stomata. Spines (fig. 62C) and glochids (fig. 62Ö) The cortical ground tissue of the stem is com- both are scabrous because of the projecting posed chiefly of large spherical cells inter- lower ends of the sclerified surface cells (123, spersed with intercellular spaces. Most of these 130). The spines are light yellow and firmly parenchyma carry on photosynthesis. Vascular bundles occur in a discontinuous ring near the center of the stem (fig. 61f ). Numerous clustered crystals also occur in the inner paren- chyma. A few large mucilage cavities contain- ing a white, dense material are present among the parenchyma. The old stem is woody. The outer, flaky sur- face consists of several layers of phellem and sclereids arising from a superficial phellogen (fig. 61G). Sclereids are arranged in tangential tiers about six cells deep. The phellem cells are cuboidal and thin walled (collapsed in fig. 61G). Underneath is a tier of large, corticallike parenchyma that connect with the ends of the rays. The phloem forms domelike tiers about 10 cells deep between the rays. The xylem is semiring-porous (fig. QIH). Vessels are very small. They are solitary, in short radial files, or in small clusters along the growth ring. Late wood vessels are slightly smaller than early wood vessels and mostly occur as long, oblique bands. Parenchyma are PN-5627 FIGURE 62.-—Lindheimer pricklypear (Opuntia lind- sparse and occur adjacent to the vessels. Fibers heimeri Engelm.). A, Overall new stem pad (X 2). 157 PN-5628 FIGURE 62.—Lindheimer pricklypear {Opuntia UndheimeH Engelm.)—Continued. B, Areole on stem {X 24). C, Spine tip (X 130). D, Glochids (X 130). E, New stem surface (X 230). 158 attached to the aréole with cork that is pro- also characters of tasajillo cactus, another duced by a hypodermal phellog-en (18). Opuntia species (fig. 61). Glochids are yellow to brown and more easily The surfaces of most young stems are either detached from the plant than the spine because green or bluish green. Ground epidermal cells it connects to the aréole with an unsclerified are smooth to slightly undulating (fig. &2E) zone of parenchyma (55, 123). At the base of (28). Rubiaceous stomata are present with sub- the aréole are long multicelled hairs, many of sidiary cells running parallel to the guard cells which have clubshaped heads (fig. 62i?). See (28). Surfaces of old stems, particularly those PN-5629 FIGURE 62.—Lindheimer pricklypear (Opuntia Undheimeri Engelm.)—Continued. F, Old woody stem surface (X 200). G, New outer stem area transection (X 85). H, New inner stem transection (X 84). /, Old outer stem area transection {X 85). 159 near or on the ground, are rough, flaky, and Cornaceae waxy (fig. 62^). Flowering Dogwood {Cornus florida L.) Stem transection Flowering dogwood grows in the Pineywoods, The young stems have a thick cuticle (about Post Oak Savannah, and Blackland Prairies of 7 /xm) on the epidermal cells (fig. 62(7) {28, Texas. It is either a large shrub or a small tree 179). Other workers {28, 179) indicate that growing to 9 m tall with a trunk 3 dm in the first layer of cells below the epidermis i.s a diameter. The crown is flat and spreading. It hypodermal layer. This layer contains numer- is a slow-growing understory species usually ous large clustered crystals. Below the hypo- found on deep, rich, moist sites. However, it dermis is a tier of about four layers of radially can be grown on upland sites where its showy flattened, thick-walled eollenchyma cells with bracts in the spring and scarlet drupes in the conspicuous intercellular pitting. Both the fall make this plant a desirable ornamental. hypodermal and eollenchyma cells are stained a dark bluish green with the fast green stain. Leaf shape and surface The hypodermis plus eollenchyma tier is con- The leaves are 8 to 15 cm long by 4 to 6 cm tinuous except for long, tubular cavities under wide, opposite, simple, and deciduous ; the shape the stomata. Below the eollenchyma are large, is ovate to elliptical, the apex acute or acumi- thin-walled parenchyma ; many are elongated nate, the margin entire or wavy, and the base radially. The vascular tissue consists of a net- wedge shaped, often inequilateral. The veins work of vascular bundles among the paren- characteristically curve toward the apex. chyma (fig. 62Í/). Clustered crystals are The upper surface is lustrous bright green. abundant, scattered in the parenchyma. Large The surface of the ground epidermal cells is mucilage cavities containing a white, dense ma- almost smooth except for fine cuticular stria- terial are present among the parenchyma. In tions (fig. 63A). Hairs, which are flat, two older, or diseased, stems such as in figure 62F, armed, and papillose, were abundant in the several layers of thin- and thick-walled phellem several leaves inspected. are produced from the division of the epidermal The lower surface is much paler green than cells (fig. 627), particularly beginning near the upper surface. It is covered with large, the aréoles {179), interconnecting ridges (fig. 63ß). Two types PN-56S0 FIGURE 63.—Flowering dogwood {Coj-nus florida L.). A, Leaf upper surface (X 240). B, Leaf lower surface (X 240). 160 of hairs are present : numerous flat, two-armed Leaf transection papillose hairs and long, pointed hairs. Long-, The lamina (fig. 63, C, D) has a thin cuticle pointed hairs are present in moderate numbers on both surfaces. Extensions of the outer sur- on the lamina and in large numbers on the face of the lower epidermal cells and cuticle midrib and large veins (not shown in photo). combine to form the interconnecting ridges. Ranunculaceous stomata are present only on The bases of two-armed hairs are present on the lower surface, and are widely scattered. the upper surfaces of both leaves, and an intact H D PN-5631 FIGURE 63.—Flowering dogwood {Cornus florida L.)—Continued. C, Leaf lamina transection {X 448). D, Leaf lamina transection showing trichome (X 228). E, Leaf midrib transection (X 105). F, Trunk periderm tran- section (X 85). 161 PN-5632 FIGURE 63. Flowering dogwood {Cornus florida L.)—Continued. G, Trunk phloem, cambium, and outer xylem transection (X 85). H, Trunk xylem transection (X 85). hair is shown on the lower surface in figure groups of large sclereids. Clustered crystals 63Z). Palisade parenchyma are one cell deep, occur in some of the outer parenchyma, and and the spongy parenchyma are loosely packed. some rhombic crystals are associated with the Leaves produced in the shade normally have sclereids. The translocating phloem, (fig. 63G) shorter palisade parenchyma than those pro- has a tier of sieve elements about six cells wide. duced in open sunlight (80, 133). Small veins The xylem is diffuse-porous (fig. 63i/). Ves- lie in the mesophyll parenchyma and do not sels are small, mostly with more than 30 perfo- contain fibers. rations (2), and almost entirely solitary except The midrib (fig. 63E) has an oval vascular for a few radial pairs. Overlapping ends of strand. The xylem and phloem form concentric solitary vessels give the appearance of a large circles. A few fibers lie outside the phloem. number of tangential pairs of vessels. Paren- Some cells outside the vascular strand seem chyma are scanty and are present either as a to be tanniferous. One small vein at the upper few paratracheal cells (seldom a sheath) next right has branched from the midrib vascular to the vessels, or apotracheal cells diffuse or in system. broken one-cell lines among the fibers. Fiber tracheids are thick walled. The rays are one- to Stem transection eight-seriate. The outer bark is grayish brown or black Blackgum (Nyssa syluatica Marsh.) and broken into small square blocks. It is a rhytidome consisting of several phellogens deep Blackgum grows in the Pineywoods, Gulf in the phloem (fig. GSi'). The phellogens pro- Prairies and Marshes, and Post Oak Savannah duce only about 6 layers of phellem and 2 to areas of Texas. Usually it is a tree growing to 10 layers of tanniferous phelloderm. The non- about 18 m with a trunk diameter of 6 to 9 dm. translocating phloem (fig. 63, F, G) contains The crown is round with conspicuously hori- parenchyma (many tanniferous) and many zontal branches. Blackgum grows best in open- 162 PN-5633 FIGURE 64.—Blaclcgum (Nyssa sylvatica Marsh.). A, Leaf upper surface (X 240). B, Leaf lower surface (X 240). C, Leaf lamina transection {X 309). ings on moist soils in swamps, bottom lands, cells lightly delineated and with fine cuticle and low sandy woodlands. striations (fig. 64A). The veins are prominent. Leaf shape and surface The lower surface is lighter green than the upper surface. The epidermal cells are slightly The leaves are 5 to 15 cm long by 2.5 to 8 cm papillose (fig. 64ß). Stomata are confined to wide, alternate, simple, and deciduous ; the shape is obovate to elliptic, the apex acute or the lower surface. The stomata were ranun- acuminate, the margin entire, and the base culaceous on the leaves inspected, whereas Met- wedge shaped, rounded, or subcordate. calfe and Chalk (.97) indicated that they tended The upper surface is shiny dark green, often to be rubiaceous. Cuticle ridges on the guard with black spots before turning red in the fall. cells partially co\'er the pores. Both long, The surface is glabrous with the epidermal twisted, scaly one-cell hairs and short, club- 163 PN-5634 FIGURE 64.—Blackgum (Nyssa sylvatica Marsh.)—Continued. D, Leaf midrib transection (X 102). E, Trunk periderm transection (X 85). F, Trunk phloem, cambium, and outer xylem transection (X 85). G, Trunk xylem transection (X 77). 164 shaped hairs were found only on the lower apotracheally diffuse among fiber tracheids. surface. Fiber tracheids are moderately thick walled. Rays are one- to four-seriate. Leaf transection The lamina (fig. 64C) has a thin cuticle on Ebenaceae both surfaces. Upper epidermal cells are much larger than the lower ones. Also, many upper Texas Persimmon epidermal cells are either entirely or half (Diospyros texana Scheele) (inner half) mucilaginous. Palisade paren- Texas persimmon grows in all areas of Texas chyma are long and one cell deep. Spongy except the Pineywoods, Rolling Plains, and parenchyma are loosely packed. The veins are High Plains (58). A map showing the major vertically transcurrent, containing a thin- infestations has been presented by Meyer (99). walled parenchyma bundle sheath (71). Fibers It is usually an intricately branched shrub or are present in the larger vascular bundles. The midrib contains a superimposed vascular strand (fig. 64D). The lower system is deeply crescent shaped. The upper vascular bundle is flattened. A tier of fibers almost completely encloses the vascular strand. Apparently in the petiole the lower crescent-shaped vascular tis- sue divides more clearly into three large bun- dles below with two small bundles in the wings (97). Stem transection The outer bark is gray, reddish brown, or black and divided by deep furrows into square blocks (64-). It is a rhytidome composed of several phellogens in the outer phloem produc- ing both four or more layers of phellem and one or two rows of phelloderm (fig. 64É'). The outside five or so rows of phellem, cells are thin walled. The inside three to five rows are thick walled (25). The outer phloem contains clusters of fibers and sclereids with rhombic crystals in more or less tangential tiers three or four cells deep among the parenchyma. Many parenchyma contain clustered crystals. The translocating phloem (fig. 64^) contains three tiers of sieve elements, three or four cells deep, separated by tiers of parenchyma. The cambium is active, and a new xylem ring is being formed. The xylem is diffuse-porous (fig. 64G). The vessels are numerous and small with about 52 perforations (161). Early wood and late wood vessels are about the same size, and they are either solitary or in small radial files, seldom with more than five cells. Some solitary vessels appear as tangential pairs because of the over- PN-5635 FIGURE 65.—Texas persimmon {Diospyros texana lapping ends. Parenchyma are scanty, either as Scheele). A, Leaf upper surface (X 220). B, Leaf scattered cells next to vessels or as a few cells lower surface (X 220). 165 PN-Ge36 FIGURE 65.—Texas persimmon (Diospyros texana Scheele)—Continued. C, Leaf lamina transection (X 218). D, Leaf midrib transection (X 175). £7, Trunk periderm, phloem, cambium, and outer xylem (X 82). 166 Leaf transection The lamina (fig. 65C) has a prominent cuti- cle on both surfaces. Upper epidermal cells are slightly larger than the lower ones. Palisade parenchyma are one or two cells deep. Spongy parenchyma are loosely to tightly packed. Large solitary crystals are common in the mesophyll; one is present at the left, and a larger one has been pulled out on the right during tissue preparation. Veins are embedded in the mesophyll, and the larger ones have some fibers. The midrib (fig. 65D) has three hairs on the upper surface. The vascular strand is round. It is composed of successive crescent- shaped tiers of xylem, phloem, and fibers. Small rhombic crystals occasionally are present in the parenchyma next to the fibers. PN-5037 Stem transection FIGURE 65.—Texas persimmon {Diospyros texana Scheele)—Continued. F, Trunk xylem transection The outer bark is gray, later flaking off in (X 85). thin layers exposing a reddish-gray bark under- neath. It arises from a phellogen forming in the tree up to about 4.5 m. However, Texas per- phloem. The phellogen produces both about simmon may grow to 8 m. Usually it produces four to eight phellem cells to the outside and several ascending stems from either the stem phelloderm to the inside (fig. 65£7). The bark base or roots. It grows in open areas on lime- peels off in late summer at a fracture in the stone soils, rocky hillsides, or on sides of phellem. Inner layers of phelloderm seem to ravines and canyons. The morphology of Texas form a continuous tier of sclereids. Nontrans- persimmon has been studied by Meyer (99). locating phloem consists of parenchyma and Leaf shape and surface small, scattered groups of sclereids; fibers ap- pear to be absent. The translocating phloem The leaves are 2.5 to 5 cm long by 1 to 2.3 region usually consists of one-third to two- cm wide, alternate, simple, tardily deciduous, thirds of the total phloem. and leathery; the shape is oblanceolate, the The xylem is diffuse- to semiring-porous apex obtuse, rounded, or notched, the margin (fig. 65F). The vessels are medium sized. They entire, and the base acute. are either solitary or in radial multiples of two The upper surface is dark green. The ground or three (rarely to five) cells. Early wood ves- epidermal cells are slightly papillose (fig. 65A). sels usually are only slightly larger and more Some leaves have long one-cell hairs, whereas numerous than late wood vessels. Parenchyma others are free of hairs on the upper surface. are abundant, occurring (1) paratracheally in The lower surface is pale green and is more one- or two-cell sheaths around the vessels, or less papillose with prominent veins (fig. (2) apotracheally forming one- or two-cell 65B). Long one-cell hairs are always present. tangential bands, and (3) marginally in one- Some leaves have few hairs, and others have or two-cell-wide bands. Fibers are thick walled. moderate (fig. 65J5) or large numbers. Many Rays are one- to three-seriate. hairs are long and twisted; others are shorter. The spherical objects in figure 65B are short- Common Persimmon stalked multicelled glands. Stomata are ranun- culaceous and occur only on the lower side. (Diospyros virginiana L.) The guard cells have raised cuticular edges that Common persimmon grows in the Piney- partially cover the pore. woods. Gulf Prairies and Marshes, Post Oak 167 Savannah, Blackland Prairies, Cross Timbers The upper surface is lustrous dark green. and Prairies, and Rolling Plains of Texas. It It is papillose with a few long, pointed one-cell normally is a tree 12 to 18 m tall with a broad, hairs (fig. 66A). The lower surface is lighter rounded crown (67). Common persimmon is green than the upper surface. It has prominent- most frequently found either as a tree in low, ly interconnecting cuticular ridges (fig. 6G, B, moist sites or as low-growing thickets in old C). Veins are prominent on both surfaces. fields. Long hairs are more numerous on the lower surface than on the upper one. Stomata are Leaf shape and surface ranunculaceous and occurred only on the lower The leaves are 8 to 15 cm long by 5 to 10 cm surface of the leaves scanned (fig. 66, B, C). wide, alternate, simple, and deciduous; the Metcalfe and Chalk {97), however, reported shape is ovate-oblong to elliptic, the apex acute that a few stomata have been found on the or acuminate, the margin entire, and the base upper surface as well. The guard cells have acute or round. cuticular ridges that partially cover the pores. /»,"- ~.J... 'V / - ** ' ''■■'' - V,.. -t- V"- J^-^ .T^'LV.: /.■M"- PN-5638 FIGURE 66.—Common persimmon {'Dios'pyros virginiana L.). A, Leaf upper surface (X 240). B, Leaf lower sur- face (X 220). C, Leaf lower surface stomata (X 540). D, Leaf lamina transection (X 200). 168 PN-BG39 FIGURE 66.—Common persimmon (Diospyros virginiana L.)—Continued. E, Leaf midrib transection (X 84). F, Trunk periderm transection {X 85). G, Trunk phloem, cambium, and outer xylem transection (X 85). H, Trunk xylem transection (X 85). 169 Leaf transection with a trunk diameter of 6 to 9 dm. The crown The leaf lamina (fig. 66D) has a moderately is open and pyramidal. White ash makes its thick cuticle on both surfaces. Most upper epi- best growth on deep, moist, fertile soils but dermal cells are larger than the lower ones. may also be grown on upland sites as an Some of the epidermal cells on both surfaces ornamental. contain dark-staining materials. Palisade pa- Leaf shape and surface renchyma are long and one or two cells deep. The leaves are 20 to 30 cm long, opposite, Spongy parenchyma are loosely packed. Many odd-pinnately compound with five to nine of the middle-sized veins are vertically trans- (mostly seven) leaflets, and deciduous. The current. leaflets are 8 to 13 cm long by 4 to 8 cm wide ; The midrib (fig. 66E) has a ridge on the the shape is ovate to oblong-lanceolate, the apex upper surface. The xylem and phloem form acute or acuminate, the margin entire or re- thick, shallowly crescent-shaped tiers. Some of motely crenate (obscurely toothed), and the the parenchyma contain rhombic and clustered base rounded to acute. crystals. The upper surface is dark green and slightly Stem transection wavy with faintly discernible veins (fig. 67A), The outer bark is dark gray, brown, or black A few long, pointed hairs (none shown) were and separated into thick, nearly square blocks present on the leaflet. The lower surface is (67), It is a rhytidome consisting of several paler green than the upper surface (fig. 67S). phellogens that produce only a few layers of The cuticle forms a network of prominent, phellem (fig. 66F). The outer, nontranslocat- interconnecting ridges (180). Numerous long, ing phloem consists of parenchyma and scat- pointed hairs are present. Peltate glands are tered solitary or groups of two or three large widely scattered (fig. 67C). They are slightly sclereids. less than twice the diameter of the stomata. The translocating phloem area (fig. 66G) The stalk is usually short, and the shield is consists of sieve elements interspersed with pa- composed of from four to eight cells. Ranun- renchyma and solitary or small groups of scle- culaceous stomata are present only on the lower reids. Many of the ray cells are tanniferous. surface. A cuticle extension partially covers the Rhombic crystals are associated with some of pores. the sclereids. Leaflet transection The xylem is semiring-porous (fig. 66, G, H) {67). Vessels are few and medium in size with The leaflet lamina (fig. 61D) has a promi- thick walls. They are either solitarj^ or in nent cuticle on both surfaces. Upper and lower radial multiples of two to five cell¿. Early epidermal cells are about the same size. Pali- wood vessels decrease gradually in size toward sade parenchyma are two or three cells deep. the outer margin of the ring. Parenchyma are The spongy parenchyma are moderately tightly abundant. Some are paratracheal forming a packed. Veins are vertically transcurrent. sheath one or two cells wide around the vessels. In the leaflet midrib (fig. 67£'), the vascular Some are apotracheal in one- or two-cell strand is closed with a flattened upper side. tangential bands. The others are marginal, The xylem seems to be superimposed with a forming a band one or two cells wide on the small upper tier and large crescent-shaped edge of the growth ring. Fibers are thick lower tier of vascular tissue. Successive tiers walled. Rays are one- to three-seriate. of phloem and fibers lie outside the xylem. A long, pointed multicelled hair is present at the Oleaceae right. White Ash (Fraxinus americana L.) Stem transection White ash grows in the Pineywoods, Gulf The outer bark is light gray to dark brown Prairies and Marshes, Post Oak Savannah, with deep fissures separating narrow ridges Blackland Prairies, and Cross Timbers and in an interlacing pattern. It is a rhytidome Prairies. It usually is a tree to 21 or 25 m tall comprised of numerous phellogens forming 170 *^' Í .^1^ '?*'*<^^^'^'i^'*^ i PN-5640 FIGURE 67.—White ash {Fraxinus americana L.)- A, Leaflet upper surface (X 200). B, Leaflet lower surface (X 200). C, Leaflet lower surface stomata and gland (X 550). D, Leaf lamina transaction (X 238). deep in the phloem. Only about three to five described by Srivastava {1-Í2) and Tepper and layers of phellem are formed (fig. 67F). Non- Hollis {15Jf). translocating phloem is composed of alternat- The xylem is prominently ring-porous with ing strata of parenchyma and fibers plus a large, thick-walled vessels (fig. 67, G, H). few sclereids {fig. 67, F, G). The translocating Early wood vessels are large, forming a band phloem tier (fig. 67G) is about 10 sieve ele- two to four vessels wide. The transition from ments wide with some scattered parenchyma the early to late wood is abrupt. Late wood {93). The structure of the cambium has been vessels are very small and are either solitary 171 PN-5641 FIGURE 67.—White ash (Fraxinus americana L.)—Continued. E, Leaf midrib transection (X 103). F, Trunk periderm and outer phloem transection (X 85). G, Trunk phloem, cambium, and outer phloem transection (X 85). H, Trunk xylem transection (X 85). 172 or in multiples of two to four cells. Paren- The upper leaf surface is dark green and chyma are moderatey abundant; they are para- minutely scabrous. The ground epidermal cells tracheal, forming a one-cell layer around most are papillose with many large glandular hairs of the early and some late wood vessels. In (fig. 68A). The enlarged bulb-shaped base of the late wood, parenchyma also may either be the hair is surrounded by a group of raised aliform or form tangential bands two to four cells. cells wide connecting the vessels. Also, margi- The lower surface is lighter green than the nal parenchyma form a tier one to three cells upper surface and usually somewhat pubescent. wide at the edge of the growth ring. Fibers It is extremely variable. In the leaf scan (fig. are medium thick walled. Rays are one- to 68ß), there are a number of long, pointed three-seriate. glandular hairs and numerous large- and small- headed capitate hairs. In the leaf used for the Verben ace ae transection, there are numerous small hairs and Whitebrush (Aloysia lycioides Cham.) multicelled glands (fig. 68C) that were not on the leaf in figure 68ß. Stomata occur only on Whitebrush grows in all areas of Texas ex- the lower surface and appear to be ranun- cept the Pineywoods, Post Oak Savannah, and culaceous; most are slightly raised above the High Plains. It is a much branched, slender, surface of the ground epidermal cells. aromatic, thicket-forming shrub 1 to 4.3 m tall. It grows on a variety of sites, including rock Leaf transection outcrops, semiarid grasslands, low places, rocky The lamina (fig. 68D) has little cuticle. creekbeds, woods, and hillsides. Upper epidermal cells are much larger than Leaf shape and surface lower epidermal cells. A one-cell layer of hypo- derm lies under the upper epidermis. Large The leaves are 0.3 to 3.3 cm long by 2 to 8 cystoliths occur under the bases of the large mm wide, decussate-opposite, simple, and decid- glandular hairs. Numerous short, pointed hairs uous; the shape is lanceolate to oblong or and small stalked hairs with pear-shaped heads elliptic, the apex acute or obtuse, the margin are present. Palisade parenchyma are three to entire or coarsely serrate, often revolute, and five cells deep. Spongy parenchyma are loosely the base wedge shaped. packed. Vascular bundles lie in the mesophyll PN-5642 FIGURE 68.—Whitebrush {Aloysia lycioides Cham.). A, Leaf upper surface (X 200). B, Leaf lower "smooth" surface (X 200). 173 and ' are surrounded by a sheath of large Stem transection parenchyma. The outer bark is tan and thin with shallow In the midrib (fig. 6SE), the vascular strand fissures separating small ridges. It is formed consists of an oval-shaped xylem with a cres- from deep phellogens producing- thin-walled cent-shaped phloem beneath. The midrib is phellem cells (fig. 687^). The nontranslocating surrounded by a sheath of large, thin-walled phloem is comprised of alternating tiers of parenchyma cells. Most of the other cells in the parenchyma and sclereids. Many rhombic crys- midrib are also large and thin walled. tals are associated with the sclereids. Trans- PN-5e43 FIGURE 68.—Whitebrush (Aloysia lycioides Cham.)—Continued. C, Leaf lower trichome-covered surface (X 500). D, Leaf lamina transection ( X 200). £", Leaf midrib transection {X 172). 174 locating phloem consists of 5 to 12 layers of broad, decussate-opposite, simple, and decid- sieve elements. uous; the shape is ovate to elliptic, the apex The xylem (fig. 68, F, G) is semiring-porous. acute or acuminate, the margin coarsely ser- Vessels are small. Early wood vessels are one or rate, and the base wedge shaped. two cells deep, and they grade gradually to the The upper surface is dark green. The surface slightly smaller late wood vessels. Many late is papillose and has some conical multicelled wood vessels are solitary, but most occur in hairs of various sizes that seem, to have two or groups up to 10 cells either in radial files or three cells (fig. 69A). Frequently the lowest in clusters. Parenchyma are exclusively para- cell is flattened. The hairs have a series of tracheal and sparse. Fibers are medium to small cells around the base. A few peltate thick walled. Rays are one- to three-seriate. glands are present. Also, two short-stalked glandular hairs are shown. The heads are col- American Beautyberry lapsed, normally they are spherical as shown in (Callicarpa americana L.) figures 6dB and 69C. American beautyberry occurs in the Piney- The lower surface is lighter green than the woods, Gulf Prairies and Marshes, Post Oak upper surface and is pubescent to the touch. Savannah, Blackland Prairies, Cross Timbers The lower surface is slightly papillose and has and Prairies, and Edwards Plateau of Texas. prominent veins (fig. 695). Large stellate hairs It is a shrub growing to 3 m tall ; usually it is with 3 to 12 arms are abundant on the lower much branched. American beautyberry grows surface, especially on the midrib and large mostly in woods and thickets on sandy to veins. Glands are abundant, and most are large, clayey soils. sessile, peltate, and multicellular. Also, there are a few glands with small multicelled heads Leaf shape and surface on short stalks (fig. 69, B, C). Stomata are ra- The leaves are 8 to 23 cm long by 4 to 13 cm nunculaceous and occur only on the lower sur- PN-5644 FIGURE 68.—Whitebruah (Aloysia lycioides Cham.)—Continued. F, Stem periderm, phloem, cambium, and outer xylem (X 85). G, Stem xylem transection (X 85). 175 PN-5645 FIGURE 69.—American beautyberry {Callicarpa americana L.). A, heat upper surface {X 110). B, Leaf lower sur- face showing trichomes {X 110). C, Leaf lower surface stomata and gland (X 550). D, Leaf lamina transac- tion showing gland ( X 408). face (fig. 69C). They are slightly raised and are larger than lower ones. Palisade paren- usually have fine cuticular striations radiating chyma are one cell (rarely tw^o) deep. Spongy outward from the sides. The guard cells have parenchyma are large and usually loosely a cuticular ridge that partially covers the pore. packed. On the lower surfaces are shown a sessile peltate gland (fig. 69Í)) and a multi- Leaf transaction cellular stellate hair (fig. GQE"). Vascular The lamina has a thin cuticle on both sur- bundles are vertically transcurrent. faces (fig. 69, D, E). Upper epidermal cells The midrib (fig. 69/^) has two mostly intact 176 /• PN-5e46 FIGURE 69.—American beautyberry {Callicarpa americana L.)—Continued. E, Leaf lamina showing trichome (X 364). F, Leaf midrib transection (X 85). 177 PN-5647 FIGURE 69.—American beautyberry {Callicarpa americana L.)—Continued. G, Stem periderm, phloem, cambium, and outer xylem transection (X 85). H, Stem xylem transection (X 83). multicellular hairs on the epidermis. The vascu- translocating phloem is a tier of sieve elements lar strand is oval. Large crescent-shaped tiers about 6 to 12 cells wide next to the cambium. of xylem and phloem comprise the bulk of the The xylem is ring- to semiring porous (fig. vascular tissue and extend about three quarters 697/). Vessels are small. Early wood consists of the way up the strand. There is a small of a band of vessels one to five cells deep at the vascular bundle at the tops of both ends ring margin. Late wood vessels are generally (wings) of the large crescent-shaped bundle. slightly smaller than the spring wood vessels Scattered thick-walled fibers almost entirely and are either solitary or in radial multiples encircle the lower two-thirds of the strand. of two to five cells. Parenchyma are para- Also, some medium, thick-walled fibers or tracheal, being sparsely distributed around the vessels. Fibers are medium thick walled. Rays collenchyma occur at the top of the strand. are one- to four-seriate. Stem transection Solonaceae The outer bark is gray to reddish brown and is somewhat roughened with small, thin scales. Berlandier Wolfberry It forms from a superficial phellogen that pro- (Lycium herlandieri Dunal var. duces about 4 to 10 layers of phellem (fig. berlandieri) 69G). Underneath is a tier of corticallike pa- Berlandier wolfberry occurs in the Gulf renchyma about 10 cells deep. The outer phloem Prairies and Marshes, South Texas Plains, consists almost entirely of parenchyma except Edwards Plateau, and Trans-Pecos Mountains for some lignified cells that are either diffuse and Basins of Texas. It is a sparingly, hori- or in more or less one-cell tangential lines. The zontally- to drooping-branched shrub, some- 178 PN-5648 FIGURE 70.—Berlandier wolfberry {Lycium herlandieri Dunal var. herlandieri). A, Leaf upper surface (X 200). B, Leaf lower surface (X 200). C, Leaf lower surface stoma (X 1,000). D, Leaf lamina transeetion {X 104). times spinose, attaining a height of 2 m. It (fig. IQB) surfaces are medium green and grows on gravelly-rocky hills, limestone and papillose with fine cuticular striations on the clay flats, alkali flats, and thickets. ground cells. Stomata are ranunculaceous and Leaf shape and surface occur on both surfaces. Figure 70C shows a further enlarged lower surface with smooth The leaves are 1 to 2.5 cm long by 2 to 3 mm guard cells and striated ground epidermal cells. wide, alternate or two or three in a cluster, No trichomes were found on either surface. and deciduous ; the shape is linear to spatulate, the apex acute to rounded, the margin entire, Leaf transeetion and the base cunéate. The lamina and margin have little cuticle Both the upper (fig. 70A) and the lower other than the striations (fig. TOO). The leaf 179 PN-5649 FIGURE 70.—Berlandier wolfberry (Lycium berlandieri Dunal var. berlandieri)—Continued. E, Leaf midrib tran- section (X 170). F, Stem periderm transection (X 77). G, Stem phloem, cambium, and outer xylem transection (X 85). H, Stem xylem transection (X 85). 180 is isobilateral, and the mesophyll parenchyma In the midrib (fig. 70E), the vascular strand are similar throughout rather than being di- contains a bicollateral bundle with the upper vided into palisade and spongy parenchyma. phloem more or less oval and the lower tier Parenchyma are moderately tightly packed shallowly crescent shaped. The xylem is shal- toward both surfaces but are loosely packed in lowly crescent shaped. The bundle has fibers the middle. Veins are numerous and small and both above and below the vascular tissue. lie in the mesophyll. Clusters of small crystals are occasionally present in the mesophyll. Stem transection The outer bark is gray and thin with narrow ridges. It is a rhytidome with several phello- gens that form deep in the phloem (fig. 70F). The phellogens only produce two or three phellem cells. Near the surface, the secondary phloem parenchyma have almost all collapsed. The translocating phloem (fig. 70G) has small sieve elements among the parenchyma in a tier of about 15 to 20 cells. Numerous crystals {crystal sand) occur in the phloem. No fibers were present in the phloem. The xylem is ring-porous (fig. 70H), but the rings are thin, and many are incomplete. Vessels are medium to small in size. Early wood vessels are mostly either solitary or with sev- eral smaller ones next to the large ones. Late wood vessels occur either in radial files or in oblique groups. Parenchyma are paratracheal as a few cells around the vessels and apo- tracheal either as scattered cells among the fibers or as one-cell tangential bands between rays. Some parenchyma are present in the ring margins as a one-cell layer. Some parenchyma contain small crystals. Fiber walls are medium thick walled. Rays are exclusively uniseriate. Compositae Sand Sagebrush (Artemisia fiUfolia Torr.) Sand sagebrush occurs in the Rolling Plains, High Plains, and Trans-Pecos Mountains and Basins of Texas. It is a rounded, freely branched shrub usually less than 1.2 m tall. It grows most often in areas of dunes or other deep, loose sand. Leaf shape and surface Leaves are 4 to 8 cm long by about 1 mm wide, alternate, simple, and deciduous ; the shape is filiform, the apex acute ; the margin of upper leaves is usually entire, whereas lower PN-5650 ones are often divided into threadlike divisions; FIGURE 71.—Sand sagebrush (Artemisia fiUfolia Torr.). A, Overall leaf surface (X 220). B, Leaf the base is slightly rounded. The leaf is more surface at edge of lobe (X 500). or less rectangular in transection with four 181 deep lobes running" the long axis of the leaf. The outer lobe surface has an elongated plate- like appearance (fig. 71, A, B, C). On top are several types of trichomes. Many short, rec- tangular hairs have a flat top, and most have collapsed sides. A few hairs have cylindrical stalks and an enlarged head (fig-. IIC). A few elongated leaflike structures also occur on top. In the lobes there is a dense concentration of multicelled leaflike structures (fig. 71, A, B, C). Leaf transection The leaf is rectangular in transection with four deep lobes (fig. IID). The top of the lobe has a thick cuticle that thins progressively toward the base. The epidermal cells also are large on top and decrease in size progressively toward the base of the lobe. Many of the top epidermal cells contain tannin. Stomata lie along the inside and base of the lobes. Meso- phyll parenchyma are one to three cells deep. PN-5G51 A large vascular bundle occurs in the center, FIGURE 71.—Sand sagebrush {Artemisia filifolia and two smaller ones occur on each side. The Torr.)—Continued. C, Leaf lobe top surface (X 500). bundles are surrounded by a sheath of large parenchyma. A resin duct occurs inside the bundle sheath of the midrib and both lateral vascular bundles. Inside the midrib sheath the xylem and phloem form straight, superimposed PN-5652 FIGURE 71.—Sand sagebrush {Artemisia filifolia Torr.)—Continued. D, Leaf midrib transection (X 116). 182 tiers, with the xylem on top. A few fibers lie surrounded by fibers. Numerous secretory cavi- both above and below the vascular tissue. More ties occur, particularly in the rays throughout fibers are present in older leaves. the phloem. The xylem is more or less diffuse-porous Stem transection with the early wood vessels being slightly The outer bark is dark gray to black with larger than the late wood vessels (fig. 71G). shallow furrows. It is a rhytidome formed by a All vessels are small. Early wood vessels occur phellogen that forms deep in the phloem (fig. singly to groups of six cells. In the late wood, 1\E). Only a few layers of phellem are pro- some groups of vessels occur in radial files one duced. The outer phloem (fig. HE) is comprised or more cells wide, and others occur more or mostly of thick tiers of fibers separated by less tangentially. Parenchyma arise sparsely thin tiers of parenchyma. The translocating around the vessels. About four layers of margi- phloem (fig. IIF) usually consists of a tier of nal parenchyma lie at the edge of the growth 10 or fewer sieve elements. The sieve elements rings. Fibers are abundant and have thick either form alternate tiers with fibers or are walls. The rays are three- to seven-seriate. PN-5653 FIGURE 71.—Sand sagebrush {Artemisia filifolia Torr.)—Continued. E, Stem periderm transection (X 71). F, Stem phloem, cambium, and outer xylem (X 71). G, Stem xylem transection (X 71). 183 PN-Be54 FIGURE 72.—Willow baccharis (Baccharis salicina Torr. & Gray). A, Leaf upper-surf ace (X 550). B, Leaf lower surface (X 500). C, Leaf lamina transection (X 170). Willow Baccharis simple, and deciduous; the shape is oblanceo- (Baccharis salicina Torr. & Gray) late-oblong, the apex obtuse to acute, the margin entire or serrate with teeth about 5 mm Willow baccharis occurs in all areas of Texas apart, mostly remote, and the base cunéate. except the Pineywoods. It is a much branched The upper surface is bright green. Both the shrub attaining- a height of 1 to 4 m. The upper (fig. 72A) and the lower (fig. 72B) sur- branches are ascending. Willow baccharis faces have numerous ranunculaceous stomata grows primarily in open areas on disturbed and more or less papillose ground epidermal old fields and along roadsides on sandy to cells. No trichomes were found on either clayey soils. surface. Leaf shape and surface Leaf transection The leaves are 2.5 to 5 cm long by 5 to 13 mm The lamina (fig. 72C) has little cuticle. The wide and more or less three veined, alternate, leaf is isobilateral with two or three palisade 184 PN-5655 FIGURE 72.—Willow baccharis {Baccharis salicina Torr. & Gray)—Continued. 2), Leaf midrib transection (X 85). E, Stem periderm transection ( X 85). F, Stem phloem, cambium, and outer xylem transection ( X 85). G, Stem xylem transection 185 parenchyma layers toward both surfaces. The tier of sieve elements 4 to 15 cells wide (fig. cells are compact except immediately beneath 72F). The ray cells enlarge toward the outside the stomata. Two or three layers of compact compared to those next to the cambium. Num- spongy parenchyma occur in the middle. Veins erous ray parenchyma in the phloem contain lie in the spongy parenchyma and are sur- needlelike crystals. rounded by a sheath of large, thin-walled pa- The xylem is ring-porous to semiring-porous renchyma cells. Fibers occur both above and (fig. 72G). Vessels are very small. Spring wood below the vascular bundle in the larger veins. vessels may be solitary, but most form groups A secretory canal lies below the lower tier of occurring either as clusters or in radial files. fibers in the largest vein. Early wood vessels grade gradually to smaller In the midrib (fig. 72Z)), the vascular strand late wood vessels. Late wood vessels form has a sheath of one or two layers of large, groups in radial, oblique, or tangential lines. thin-walled parenchyma. Xylem is more or less Parenchyma are moderate in numbers, occur- oval, and a flattened, crescent-shaped phloem ring paratracheally around the vessels. Also, in lies beneath. Numerous fibers form tiers both the late wood, apotracheal parenchyma often above and below the vascular bundle. A secre- form more or less tangential or oblique bands tory canal is present in one of the veins to the connecting the vessels. Some cells on the ring left of the midrib. margin appear to be parenchyma. Fibers have thick walls. Ray are one- to four-seriate. Stem transection The outer bark is light to dark brown and Tarbrush {Flourensia cernua DC.) thin with shallow fissures separating narrow Tarbush occurs in the Edwards Plateau and ridges. It is a rhytidome formed from phel- Trans-Pecos Mountains and Basins of Texas. logens arising in the phloem (fig. 12E}. It is a densely leafy, much branched shrub Usually only a few layers of phellem are pro- growing to 2 m tall. It grows largely on desert duced. Nontranslocating phloem, consists mostly and semiarid soils of valleys, mesas, and flats. of parenchyma with many fibers that form more or less rings around the parenchyma Leaf shape and surface (fig. 72, E, F). The fiber rings lie more or less The leaves are 1.8 to 2.5 cm long by 0.5 to in tangential strata. Translocating phloem is a 1.3 cm wide, alternate, simple, persistent, and PN-5G5fi FIGURE 73.—Tarbush (Flourensia cernua DC). A, Leaf upper surface {X 120). B, Leaf lower surface (X 120). 186 aromatic with an odor of tar ; the shape is parenchyma lie in the center. The veins are elliptic to ovate, the apex acute, the margin vertically transcurrent with a sheath of large, entire, and the base acute. thin-walled parenchyma surrounding the vascu- The upper surface is deep green ; the lower lar bundle. Little if any fibers or collenchyma surface is paler. Both the upper (fig. 73A) accompany the vascular bundle. A large resin and lower (fig. 73ß) surfaces have stomata duct lies in one vein below the phloem. and trichomes and are slightly papillose. The The midrib (fig. 73Z)) is vertically trans- cuticle of the ground epidermal cells is either current with a sheath of one to three layers of smooth or finely striated. Stomata appear to large thin-walled parenchyma. In the vascular be ranunculaceous, and the guard cells have bundle the xylem is round, and the phloem is small cuticular ridges that partially cover the either flat or slightly crescent shaped. Resin pore. ducts are present in some midribs, as well as in Two types of multicelled hairs were found smaller veins. on both surfaces. The larger one has a base Stem transection that is slightly bulbous with two or three shal- low constrictions in the middle; the tip of the The outer bark is gray to whitish, thin, and hair narrows to a point and has fine pro- somewhat striate. It is a rhytidome with sev- tuberances. The second type of hair is short, eral phellogens cutting off tiers of secondary generally pointed, and with three to six shallow phloem (fig. 73^"). Only a few layers of phellem constrictions at the transverse cell walls. Tar- are produced. Nontranslocating phloem (fig. like material with debris frequently is present 73, E, F) consists mostly of parenchyma but such as in the upper right corner of figure 73A does contain tangential tiers of fibers about six and the left side in figure 73¿?. layers wide alternating with tangential rows of resin ducts. Both the fiber groups and resin Leaf transection ducts lie between the rays. The translocating The lamina (fig. 73C) has a moderately thin phloem is 5 to 15 sieve elements deep next to cuticle. The leaf is isobilateral with usually the cambium (fig. 73F). three layers of palisade parenchyma toward The xylem is ring-porous (fig. 73G). Vessels each surface. One to three layers of spongy are small. Spring wood vessels are solitary, in V"' PN-5657 FIGURE 73.—Tarbush {Flourensia ceimua DC.)—Continued. C, Leaf lamina transection (X 166). D, Leaf midrib transection (X 85). 187 PN-5658 FIGURE 73.—-Tarbush {Fhurensia cemua DC.)—Continued. E, Stem periderm transection (X 85). F, Stem phloem, cambium, and outer xylem transection {X 77). G, Stem xylem transection (X 85). small clusters, or in radial files to five cells tial tiers. Parenchyma are abundant, forming deep. Late wood vessels may be the same size one-cell sheaths around many vessels and or grade gradually smaller toward the outside broad tangential bands enclosing the late wood of the ring compared to the early wood vessels. vessels. Vessels in the older rings are usually Late wood vessels occur singly or in small filled with tanniferous material. Fibers are groups of diverse shapes, frequently in tangen- very thick walled. Rays are two- to five-seriate. 188 GLOSSARY AbaxiaU side away from the axis (lower). Decussate, arrangement of leaves where pairs arise Acuminate, an acute leaf apex whose sides are concave. alternately at right angles. Acute, a leaf ending in an angle less than 90°. Deltoid, equilaterally triangular. Adaxial, side toward the axis (upper). Diffuse parenchyma, axial wood parenchyma as single Albuminous cells, certain ray and phloem-parenchyma cells or as strands distributed irregularly among cells in gymnosperms that are closely associated fibers away from vessels, as seen in transection. morphologically and physiologically with the sieve Diffuse-porous wood, xylem in which vessels are dis- cells. tributed fairly uniformly throughout a growth layer Apotracheal parenchyma, marginal, banded, or diffuse or change only gradually in size from early to late axial parenchyma of the xylem independent of the wood. vessels. Doubly compound leaf, a leaf with two divisions of Appressed, closely and flatly pressed against. branching resulting in leaflets supported on rachises Axial parenchyma, longitudinal parenchyma in second- that in turn are supported by the petiole. ary vascular tissues as contrasted with ray-paren- Doubly-serrate, having large sharp teeth pointing chyma. forward with each one also toothed. Bark, a nontechnical term applied to all secondary tis- Early wood, the xylem formed in the first part of the sues outside the vascular cambium or xylem of stems growth layer that is less dense and having larger and roots. cells than in the late wood. Bicollateral vascular bundle, a bundle having phloem Elliptical, in the form of a flattened circle usually on two sides of the xylem. more than twice as long as broad. Bilateral leaf, a leaf with palisade parenchyma on the Emarginate, with a small notch at the apex. upper side and spongy parenchyma on the lower side Entire, having a margin without toothing or division. of the lamina. Epidermis, the outermost layer of cells of primary Bipinnate leaf, a compound leaf that has twice pinnate origin. branching. Epithelial cell, a cell, usually secretory, in the compact, Bundle sheath, a layer or layers of cells, usually paren- apparently physiologically specialized tissue covering chyma, enclosing a vascular bundle. a free surface or lining a cavity. Cambium, a meristem consisting of one layer of initials Fascicle, a cluster or bundle. and their undifferentiated derivatives arranged in Fascicle sheath, the ensheathing tissue formed at the orderly parallel, radial files that give rise to the base of a needle cluster in the genus Pinus. phloem and xylem. Fiber, an elongated tapering sclerenchyma cell with a Clustered crystal (or druse), a globular compound more or less thick secondary wall, with or without crystal with many components projecting from its sur- lignin. face. Fiber tracheid, a fiberlike tracheid, commonly thick Collenchyma, supporting tissues composed of more or walled, in xylem with a small lumen, pointed ends, less elongated living cells with unevenly thickened and bordered pits having lenticular to slitlike aper- walls. tures. Companion cell, a specialized parenchyma cell in the Fusiform cell, an elongated cell with tapering ends. phloem of angiosperms arising from the same mother Fusiform initial, an elongated cell with tapering ends cell as the sieve tuber member. in the vascular cambium that gives rise to the second- Compound leaf, a leaf with two or more separate leaf- ary xylem and secondary phloem tissues other than lets. related to the rays. Cordate, heart shaped. Gelatinous fiber, a fiber having a more or less unligni- Cortex, the primary tissue region consisting of paren- chyma between the epidermis and vascular systems. fied inner wall gelatinous in appearance. Crenate, a margin with scalloped or rounded teeth. Glabrous, a surface without pubescence. Cunéate, wedge shaped with the narrow part at point Gland, a multicellular secretory structure. of attachment. Glaucous, covered with a white, waxy bloom. Cuticle, a layer of waxy material, cutin, more or less Globose, globular or spherical. impervious to water on the outer wall of epidermal Glochid, a minute prickle with hooklike projections in cells. cacti. Cystolith, a concentration of calcium carbonate on an outgrowth of the cellulose wall. Guard cell, two cells of a stoma that open or close the Deciduous, falling off as leaves in the fall, not ever- stomatal opening by changes in turgidity. green. Heartwood, the inner layers of xylem that in the grow- 189 ing tree have ceased to contain living cells and in of a leaf arranged with their long axes perpendicular which the energy reserve materials have been either to the surface of the leaf. recovered or converted into more durable substances; Palmate, a leaf having the lobes or divisions radiating generally darker in color than sapwood. from a common point of origin. Heterogeneous ray, in conifers, a ray composed of both Papillose, bearing rounded cell walls or small protuber- parenchyma and tracheids; in porous wood, a ray ances on a leaf surface. comprised of both erect and procumbent cells. Paratracheal parenchyma, axial parenchyma of the Homogeneous ray, a ray composed wholly of but one xylem associated with vessels and other tracheary type of cell. elements. Hypodermis, the tissue immediately underlying the Parenchyma cell, usually refers to a cell with a live epidermis, especially if different from tissues deeper nucleate protoplast concerned with one or more of the in the plant. various physiologic activities in plant; it may vary Idioblast, a special cell in a tissue that markedly differs in size, form, and wall structure. in form, size, or contents from other cells in the same Peltate gland, a trichome, consisting of a discoid plate tissue. of cells borne on a stalk or attached directly to the Isobilateral leaf (isolateral), a leaf in which palisade foot. parenchyma occurs under both the upper and lower Perforation plate, part of the wall of a xylem vessel epidermis and with spongy parenchyma in the middle. member that is perforated, usually on the end wall. Lanceolate, shaped like a lance head. Periderm, secondary protective tissues including the Lamina, part of the leaf blade other than the midrib phellem and phelloderm; it is derived from the phel- and the margin. logen that replaces the epidermis in stems and roots. Late wood, the xylem formed in the later part of the Persistent, pertaining to leaves that are evergreen or growth layer that is more dense and has smaller cells remain on the tree over winter. than in the early wood. Phellem, nonliving cells in the periderm formed to the Leaf, the usually thin and expanded organ borne lat- outside by the phellogen. erally on the stem, including the blade, petiole, and Phelloderm, a tissue of thin-walled cells in the periderm stipules. formed to the inside by the phellogen. Leaflet, the blade of a singly or doubly compound leaf. Phellogen, the cork cambium or dividing layer of cells Leucobalanus, the white oak group. that forms the outer protective tissue (periderm) of Libriform fiber, a long fiber in the xylem with pointed stems and roots, consisting of phellem to the outside ends and simple pits and usually with thick walls. and phelloderm to the inside. Linear, long and narrow. Phloem, the principal food-conducting tissue of the Lithocyst, a cell containing a cystolith. plant that is generally composed of sieve elements, Lobe, any projecting segment or division of an organ parenchyma, and fibers. usually rounded or obtuse. Pinnate, descriptive of compound leaves with the leaf- Lumen, the cavity of a cell. lets arranged on opposite sides along a common rachis. Margin, the edge of a plane organ (leaf). Pore, opening, as of a vessel in the xylem as seen in Marginal parenchyma, axial xylem parenchyma cells transection, or between two guard cells of a stoma. occurring either singly or in continuous layers that Punctate, dotted with depressions or translucent inter- are produced at the beginning or end of the radial nal glands or colored spots. growth of a season. Rachis, the axis of a compound leaf. Midrib, the central vein of a leaf. Radial section, a longitudinal section cut along a Mucronate, a leaf or cone scale apex with a short, radius of a cylindrical body such as that of a root or narrow, and abrupt tip. stem. Mucilage cell, a cell containing mucilage, gum, or Ranunculaceous stomata, stomata surrounded by cells similar carbohydrate material. indistinguishable in size, shape, or form from the Needle, a stiff, linear leaf, as in the Pinaceae. ground epidermal cells. Node, that part of the stem at which one or more leaves Raphid, a needle-shaped crystal usually occurring with are attached. others in a closely packed bundle. Nontranslocating phloem, the outer region of the Ray, a panel of tissue formed by the cambium and phloem containing parenchyma and usually fibers that extending radially in the secondary xylem and second- does not participate in the movement of foods. ary phloem of the stem and root. Oblanceolate, lanceolate with the broadest part toward Ray initial, a rectangular cell in the vascular cambium the apex. that gives rise to ray cells of the xylem and phloem. Oblique, slanting or with unequal sides. Ray parenchyma, parenchyma cells in secondary tissues Obovate, inverted ovate. that are components of a vascular ray. Obtuse, an angle of 90° or more. Ray tracheid, a tracheid forming part of a ray in Opposite leaves, two leaves attached to opposite sides certain conifers. at the same node. Resin duct, a duct of schizogenous origin lined with Orbicular, approximately circular in outline. epithelial cells and containing resin. Ovate, egg shaped in outline, with the broader end Rhytidome, outer protective tissue consisting of one closer to the stem. or more periderms and the cortical or secondary Palisade parenchyma, elongated mesophyll parenchyma phloem isolated by the periderms. 190 Ring-porous wood, xylem in which the vessels of the Spine, modification of a stipule, petiole, or branch to early wood are distinctly larger than those of the form a hard, woody, sharp-pointed structure. late wood and form a well defined ring as seen in Spongy parenchyma, leaf mesophyll of varying shapes transection. with conspicuous intercellular spores. Rubiaceous stomata, a type of stomata accompanied on Stellate, star shaped. either side by one or more subsidiary cells parallel Stem, main axis, usually above ground, of the plant to the long axis of the guard cells. arising from its roots. Sapwood, peripheral portion of xylem in woody plants Stoma (pi. stomata), an opening in the epidermis and containing living cells with food reserve material and the two guard cells surrounding it. usually lighter in color than heartwood. Subsidiary cell, an epidermal cell associated with the Scabrous, rough to the touch owing to the structure guard cells of a stoma but morphologically distin- of the epidermis or presence of short stiff hairs. guishable from the epidermal ground cells. Scalariform (perforation plate), a type of multi- Tangential section, a longitudinal section cut at right perforate plate in xylem vessels in which elongated, angles to a radius. parallel perforations occur between bars. Thorn, a sharp-pointed modified branch. Sclereid, a short, roughly isodiametric cell with thick, Tomentose, densely hairy, usually matted. lignified secondary walls and prominent pits. Tracheid, a long, fiberlike, lignified cell with bordered Sclerenchyma, fibers or sclereids having a supporting pits and imperforate extremities; the principal longi- function that are variable in form and size having tudinal element of coniferous xylem and sometimes more or less thick, often lignified secondary walls. present in the early wood zone of ring-porous woods. Secretory cell, a living cell specialized with regard to Transection, a cross section taken perpendicularly to secretion or excretion of one or more usually organic the longitudinal axis. substances. Translocating phloem, the region of the phloem that Secretory duct, a duct, schizogenous in origin and con- contains sieve elements that translocate food materials taining a secretion derived from epithelial cells lining in the plant. the duct. Trichome, an outgrowth of the epidermis, variable in Semiring-porous wood, xylem in which the vessels di- shape, size, and function including hairs, glands, and minish gradually in diameter across the growth ring scales. as viewed in transection. Truncate, ending abruptly, as if cut off transversely. Septate fiber, a fiber with thin transverse walls that Tylosis (pi. tyloses), in xylem, the outgrowth from a form after the cell develops a secondary wall thicken- ray or axial parenchyma cell through a pit cavity in ing. a vessel wall partially or completely blocking the Seriate, disposed in series of rows. lumen of the vessel. Serrate, having sharp teeth pointing forward. Undulate, with a wavy surface or margin. Sessile, attached directly by the base, not stalked. Vascular bundle, a strandlike part of the vasculf>r sys- Sieve cell, a type of sieve element in gymnosperm tem composed of xylem and phloem in the stem and phloem that has relatively undifferentiated sieve areas leaf. on all walls with 'narrow pores and thin connecting Vein, a strand of vascular and supporting tissue in the strands. leaf. Sieve tube, a series of sieve tube members in angio- Vertically transcurrent vein, a type of vein structure sperm phloem arranged end to end and connected in leaves in which the vascular strand is connected to through sieve plates. epidermal cells of both surfaces by fibers, coUen- Simple leaf, a leaf in one unit, not compound. chyma, or other cells other than mesophyll. Xylem, the principal water and mineral conducting Simple perforation plate, an end plate of a secondary tissue in the plant; it is also important for support xylem vessel member with an unbridged opening. and food storage. Sinuate, deeply or strongly wavy margin. Xylem vessel, a tubelike series of elongated vessel Spatulate, gradually narrowed downward from a members with the common walls having perforated rounded summit. ends. 191 PHOTOGRAPH SYMBOL IDENTIFICATION LIST c Cambium L Leaf S Spine CL Collenchyma LT Leaf trace se Sclereid CO Cortex M Mesophyll SE Secretory cell CR Crystal MC Mucilage cavity SG Salt gland CY Cystolith MR Midrib SP Spongy parenchyma E Epidermis P Parenchyma ST Stoma EN Endodermis PG Phellogen sv Sieve cell F Fiber PH Phloem T Tracheid G Gland PL Phellem TT Transfusion tissue GL Glochid PP Palisade parenchyma V Vein GR Growth ring R Ray VB Vascular bundle H Hair RC Raphid crystals X Xylem HY Hypodermis RD Resin duct XV Xylem vessel 192 LITERATURE CITED (1) Abbe, L. B., and Crafts, A. S. 1939. Phloem of Agaveae). J. Linn. Soc. London Bot. Ç>Q: 157- white pine and other coniferous species. Bot. 179. Gaz. Chicago 100: 695-722. (18) Boke, N. H. 1944. Histogenesis of the leaf and (2) Adams, J. E. 1949. 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Gray, 4 Gerds canadensis L., 4 Honeylocust, 4, 10, 107 Acacia rigidula Benth., 4, 104 Cherry, black, 4, 10, 95 Hophornbeam, eastern, 3, 9, 44 Aceraceae, 5, 10, 134 Chinaberry, 5,10 Hornbeam, American, 3, 9, 42 Acer negundo L., 5,134 Chinquapin, allegeny, 3, 9 Huisache, 4, 10, 102 Acer ruhrum L., 5, 137 Ghionanthus virginicus L., 5 Ilex opaca Ait., 5,130 Acer saccharum Marsh., 5, 138 Colima, 5, 10, 120 Ilex vomitoria Ait., 5, 132 Agarito, 4, 9, 78 Colubrina, Texas, 5, 10, 142 Ivy, poison, 5, 10, 125 Agave lecheguilla Torr., 3, 23 Golubrina texensis (Torr. & Gray) Juglandaceae, 3, 9, 32 Aider, hazel, 3, 9 Gray, 5,142 Juglans nigra L., 3, 37 Alnus serrulata (Ait.) Willd., 3 Compositae, 5,11, 181 Juniperus virginiana L., 3, 12 Aloysia lycioides Cham., 5, 173 Condalia, lotebush, 5, 10, 144 Karwinskia humboltiana (R. & S.) Amaryllidaceae, 3, 9, 23 Gondalia obtusifolia (Hook.) Zuce, 5,146 Anacardiaceae, 5, 10,121 Weberb., 5, 144 Larrea tridentata (DC.) Coville, Anaqua, 5, 10 Cornaceae, 5, 10, 160 4,115 Aquifoliaceae, 5, 10, 130 Gornus florida L., 5, 160 Lauraceae, 4, 9, 83 Artemisia filifolia Torr., 5,181 Corylaceae, 3, 9, 39 Lechuguilla, 3, 9, 23 Ash, white, 5,10, 170 Cottonwood, eastern, 3, 9, 25 Leguminosae, 4, 10,100 Baccharis, willow, 5, 11, 184 Coyotillo, 5, 10, 146 Liliaceae, 3, 9, 19 Baccharis salicina Torr. & Gray, Grataegus marshallii Eggelst., 4, 93 Lime pricklyash, 5, 10,120 5,184 Grataegus viridis L., 4 Liquidambar styraciflua L., 4, 87 Baldcypress, 3, 9 Creosotebush, 4, 10, 115 Liriodendron tulipifera L., 4 Basswood, American, 5, 10, 149 Cyrilla, swamp, 5,10,127 Lycium berlandieri Dunal var. Beautyberry, American, 5, 10, 175 Cyrillaceae, 5, 10,127 berlandieri, 5,178 Beech, American, 3, 9 Gyrilla racemiflora L., 5, 127 Madura pomifera (Raf.) Schneid., Berberidaceae, 4, 9, 78 Diospyros texana Scheele, 5,165 4,72 Berheris trifoliolata Moric, 4, 78 Diospyros virginiana L., 5, 167 Magnolia, southern, 4, 9, 81 Betula nigra L., 3, 39 Dogwood, flowering, 5, 10, 160 Magnolia, sweetbay, 4, 9 Bignoniaceae, 5,10 Ebenaceae, 5, 10, 165 Magnoliaceae, 4, 9, 81 Birch, river, 3, 9, 39 Ehretia anacua (Berl.) I. M. Magnolia grandiflora L., 4, 81 Blackgum, 5, 10, 162 Johnston, 5 Magnolia virginiana L., 4 Blackhaw, rusty, 5,10 Elm, American, 4, 9 Maple, red, 5, 10,137 Boraginaceae, 5, 10 Elm, cedar, 4, 9, 71 Maple, sugar, 5, 10,138 Boxelder, 5, 10, 134 Elm, winged, 4, 9, 68 Melia azedarach L., 5 Buckthorn, Carolina, 5,10 Fagaceae, 3, 9, 46 Meliaceae, 5, 10 Bumelia, gum, 5, 10 Fagus grandifolia Ehrh., 3 Mescalbean, 4,10, 112 Bumelia lanuginosa (Michx.) Pers., Flourensia cernua DC, 5,186 Mesquite, honey, 4,10, 109 5 Fraxinus americana L., 5,170 Moraceae, 4, 9, 72 Cactaceae, 5, 10, 154 Fringetree, white, 5, 10 Morus rubra L., 4, 76 Cactus, tasajillo, 5, 10, 54 Gleditsia triacanthos L., 4, 107 Mulberry, red 4, 9, 76 Callicarpa americana L., 5, 175 Granjeno, 4, 9, 66 Myricaceae, 3, 9, 30 Caprifoliaceae, 5, 10 Greenbrier, saw, 3, 9, 19 My rica cerifera L., 3, 30 Carpinus caroliniana Walt., 3, 42 Guajillo, 4, 10, 100 Nyssa aquatica L., 5 Gary a cardiformis (Wangenh.) K. Guayacan, 4, 10, 117 Nyssa sylvatica Marsh., 5, 162 Koch, 3 Hackberry, sugar, 4, 9, 64 Oak, black, 4, 9 Gary a illinoensis (Wangenh.) K. Halesia Carolina L., 5 Oak, blackjack, 3, 9, 52 Koch, 3, 32 Hamamelidaceae, 4, 9, 87 Oak, bur, 3, 9 Gary a ovala (Mill.) K. Koch, 3 Hawthorn, green, 4, 10 Oak, chinquapin, 3, 9 Garya tomentosa Nutt., 3, 34 Hawthorn, parsley, 4, 10, 93 Oak, live, 4, 9, 61 Gastanea pumila (L.) Mill., 3 Herculesclub, 5, 10 Oak, over cup, 3, 9 199 Oak, post, 4, 9, 59 Prunus serótina Ehrh., 4, 95 Smilax bona-nox L., 3, 19 Oak, southern red, 3, 9, 49 Quercus alba L., 3, 46 Solonaceae, 5, 10, 178 Oak, swamp chestnut, 3, 9 Quercus falcata var. falcata Michx., Sophora secundiflora (Ortega) Lag., Oak, water, 3, 9, 55 3,49 4,112 Oak, white, 3, 9, 46 Quercus lyrata Walt., 3 Styracaceae, 5,10 Oak, willow, 4, 9 Quercus macrocarpa Michx., 3 Sugarberry, 4, 9, 64 Oleaceae, 5,10 170 Quercus marilandica (Muenchh.), Sumac, shining, 5,10, 121 Opuntia leptocaulis DC, 5, 154 3,52 Sweetgum, 4, 9, 87 Opuntia lindheimeri Engelm., 5, 157 Quercus michauxii Nutt., 3 Sycamore, American, 4, 9, 90 Osageorange, 4, 9, 72 Quercus muehlenbergii Engelm., 3 Tamaricaceae, 5, 10,151 Ostrya virginiana (Mill.) K. Koch, Quercus nigra L., 3, 55 Tamarix pentandra Pall., 5, 151 3,44 Quercus phellos L., 4 Tarbush, 5, 11, 186 Palmae, 3, 9, 17 Quercus stellata (Wangenh.), 4, 59 Tasajillo cactus, 5, 154 Palmetto, dwarf, 3, 9,17 Quercus velutina Lam., 4 Taxodium distichum (L.) Richard, 3 Parkinsonia aculeata L., 4 Quercus virginiana Mill., 4, 61 Tilia americana L., 5, 149 Pecan, 3, 9, 32 Redbay, 4, 9, 83 Tiliaceae, 5, 10,149 Persea borbonia (L.) Spreng., 4, 83 Redbud, eastern, 4, 10 Tuliptree, 4, 9 Persimmon, common, 5, 10, 167 Redcedar, eastern, 3, 9, 12 Tupelo, water, 5, 10 Persimmon, Texas, 5, 10, 165 Retama, 4, 10 Ulmaceae, 4, 9, 64 Pinaceae, 3, 9, 12 Rhamnaceae, 5, 10, 142 Ulmus alata Michx., 4, 68 Pine, loblolly, 3, 9, 15 Rhamnus caroliniana Walt., 5 Ulmus americana L., 4 Pine, longleaf, 3, 9 Rhus copallina L., 5, 121 Ulmus crassifolia Nutt., 4, 71 Pine, shortleaf, 3, 9 Rhus radicans L., 5, 125 Verbenaceae, 5, 10,173 Pine, slash, 3, 9 Rosa bracteata Wendl., 4, 97 Viburnum rufidulum Raf., 5 Pinus echinata Mill., 3 Rosaceae, 4,10, 93 Walnut, black, 3, 9, 37 Pinus elliottii Engelm., 3 Rose, Macartney, 4, 10, 97 Waxmyrtle, southern, 3, 9, 30 Pinus palustris Mill., 3 Rutaceae, 5,10, 120 Whitebrush, 5, 10, 173 Pinus taeda L., 3,15 Sabal minor (Jacq.) Pers., 3, 17 Willow, black, 3, 9, 28 Platanaceae, 4, 9, 90 Sagebrush, sand, 5,-11, 181 Wolfberry berlandier, 5, 10, 178 Platanus occidentalis L., 4, 90 Salicaceae, 3, 9, 25 Yaupon, 5, 10, 132 Populus deltoides Marsh., 3, 25 Salix nigra Marsh., 3, 28 Yucca, small soapweed, 3, 9, 21 Porlieria angustifolia (Engelm.) Saltcedar, 5,10, 151 Gray, 4, 117 Sapotaceae, 5, 10 Yucca glauca Nutt., 3, 21 Pricklypear, Lindheimer, 5, 10, 157 Sassafras, 4, 9, 85 Zanthoxylum clava-hercules L., 5 Prosopis juliflora (Swartz) DC. Sassafras albidum (Nutt.) Nees, Zanthoxylum fagara (L.) S'arg., var. glandulosa (Torr.) Cockerell, 4,85 5,120 4,109 Silverbell, Carolina, 5, 10 Zygophyllaceae, 4,10, 115 200 •d U. S. GOVERNMENT PRINTING OFFICE : 1978 O - 251-867 U. s. DEPARTMENT OF AGRICULTURE AGRICULTURAL RESEARCH SERVICE HYATTSVILLE, MARYLAND 20782 POSTAGE AND FEES PAID U. S. DEPARTMENT OF OFFICIAL BUSINESS AGRICULTURE PENALTY FOR PRIVATE USE, $300 AGR 101