Desert Plants, Volume 5, Number 4 (Winter 1984)

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Publisher University of Arizona (Tucson, AZ)

Journal Desert Plants

Rights Copyright © Arizona Board of Regents. The University of Arizona.

Download date 23/09/2021 10:47:41

Link to Item http://hdl.handle.net/10150/552238 Volume 5, Number 4

Desert Published by The University of Arizona for the Plants Boyce Thompson Southwestern Arboretum. Editorial -Life Forms of Desert Plants 130 A Classification of Life Forms of the Sonoran Desert, With Emphasis on the Seed Plants and Their Survival Strategies 131 F. S. Crosswhite and C. D. Crosswhite The Acanthaceae of the South- western United States 162 T. F. Daniel New Plant Records From the Sonoran Desert 180 G. Yatskievych and P. C. Fischer Publication of Dr. Howard Scott Gentry's Book Agaves of Continental North America by the University of Arizona Press 191 Crassulacean Acid Metabolism 192

Tallest known Boojum Tree (Idria columnaris), over 81 feet high, with a massive Cardón Pelón (Pachycereus pringlei) at Montevideo Canyon, north of San Borja, Baja California del Norte. Photo by Mark Dimmitt. See article on life forms, pg. 131. 130 Desert Plants 5;41 Winter 1984

Volume 5, Number 4, 1984 Desert Plants Published by The University of Arizona for the Boyce Thompson Southwestern Arboretum A quarterly journal devoted to broadening knowledge of P.O. Box AB, Superior, Arizona 85273 plants indigenous or adaptable to arid and sub -arid regions, to studying the growth thereof and to encouraging an The Boyce Thompson Southwestern Arboretum at Superior, appreciation of these as valued components of the landscape. Arizona, is cooperatively managed by The Arizona State Parks Board, The Boyce Thompson Southwestern Arboretum, inc., and The University of Arizona. Frank S. Crosswhite, editor

Editorial

Life Forms of Desert Plants. With this issue we present germplasm, we have the distinct opportunity of breeding new an illustrated classification of the life forms of Sonoran Desert life form characteristics into already established crop plants seed plants. These "life forms" are actually much more than the originating outside of the desert! simple hodge -podge of shapes and structures that they might By eventually understanding the successful "ways of living" at first appear. In reality they represent important "ways of of plants in the desert we will have a much firmer basis for living" which we might term strategies for survival. In a world genetic engineering than would have otherwise been possible. too often filled with pessimism, our minds too frequently are A platycaulescent shrubby stem succulent can produce large flooded with talk of economic uncertainties, sinking water quantities of sugar and biomass under agriculturally unfavor- tables, escalating utility rates, possible oil embargos, and fear able conditions. Although we may not particularly like the of "The Day After." But a consideration of desert life forms biomass that any one species in this life form produces, we speaks to us only of optimism. We dare our subscribers to read need to look beyond species to the life form itself, -there the following article and feel anything other than a sheer sense would seem to be no reason why we should not manipulate the of exhilaration for the triumph of the various life forms over life form to produce something which we do want! the harsh and rigorous hazards that they have faced. The few life forms which we fully exploit today happen to Not only have plants been able to adapt to the Sonoran be ones which our agricultural ancestors domesticated Desert, but they have found at least 29 major ways to do so! We ;mostly in temperate regions) in the dim and distant past. are only now beginning to scratch the surface in understand- Although the plants of the Sonoran Desert have existed for ing how these life forms function. We have thus far signifi- millenia, it is our present generation and those of the future cantly exploited only two or three such life forms for food, which will bring an appropriate blend of technology and fiber, energy and other useful goods. True, many of the other understanding to bear on the fascinating possibilities of life forms have been utilized in some way by Indians and early obtaining good from these fantastic life forms! This origi- settlers. But the fantastic germplasm of most life forms has not nally was, and continues to be, the most basic goal of the been manipulated in the slightest by plant scientists! And Boyce Thompson Southwestern Arboretum. even beyond what nature has provided in Sonoran Desert Cross white and Crosswhite Desert Life Forms 131

Taxonomists have published large numbers of scientific A Classification of articles, monographs and books attempting to classify the creatures which live on earth. Paradoxically, although form (morphology) has been the criterion most widely used by Life Forms of the taxonomists to separate the various types of life (creatures) one from the other to produce classification schemes, rela- Sonoran Desert, With tively little attention has been devoted to classifying "life forms" per se. Perhaps this has resulted from a tendency to emphasize phylogenetic reconstruction in preference to the Emphasisonthe Seed importance of form in relation to function in life. Indeed taxonomists have traditionally studied preserved (dead) speci- Plants and Their mens from which it can be notoriously difficult to make interpretations relating to functional adaptations. The classi- Survival Strategies fication of life forms is only superficially taxonomic. To classify them it is necessary to understand them. To under- stand them we need to know about their physiological ecology. In this article, "life form" is not used as a synonym for "creature" or "organism," but rather in the sense of "form of life," Frank S. Crosswhite or even "form of living," with clear functional, physiological and Carol D. Crosswhite and ecological connotations. The distinctions between a life form classification and a phylogenetic one may sometimes be Boyce Thompson Southwestern Arboretum blurred. Although there is no theoretic reason that they should (or should not) necessarily coincide, sometimes they do. Monophylesis results when a single life form diverges into two over time. Polyphylesis occurs when separate life forms converge into one. Since phylogenetic classifications allow only for monophylesis (unless actual hybridization has oc- curred), they are based on divergence rather than convergence. Therefore a life form classification will diverge from a phy- logenetic classification in the degree to which the life forms themselves have undergone convergence. Likewise, the two kinds of classifications will converge in the degree to which the life forms themselves have undergone divergence. The distinctions between a life form classification and a phylogenetic one are perhaps easier to see in the plant king- dom than in the animal kingdom. For instance, numerous plant families have independently given rise to species with the typical succulent life form based on crassulacean acid metabolism (see back cover of this Desert Plants). Like- wise, distantly related plant families have independently given rise to species with the deciduous tree life form based on leaf abscission and massive secondary xylem formation. Sometimes people are startled to learn that a tiny weed is hereditarily more closely related to some huge tree than that tree is related to another huge tree which superficially looks the same! In such a case the two trees may have an identical life form while having quite different genes and chromosomes. The hydrophytic algal life form also appears to be highly polyphyletic. Parasites have arisen in many independent plant lines. We could go on for many pages with similar examples. Among animals, life forms are perhaps somewhat more monophyletic. For example, we know of no fish which have developed feathers, no parasitic elephants, no swimming flies, no birds which burrow through soil like earthworms, no snakes with wings, no flying turtles, etc. True, penguins, whales and bats have departed from the respective norms of their relatives, converging to some extent with other life forms, but they seem to be exceptions to the general state in the animal kingdom. Therefore, a classification of animal life forms perhaps coincides more closely with their true phylo- geny than does a similar classification of plant life forms. Representative hot -season therophyte: Summer Representative bulb geophyte: Mariposa Lily Poppy (Kallstroemia grandiflora) and Trailing Four O'clock (Calochortus kennedyi) at King Canyon near Tucson, (Allionia incarnata) in the San Simon Valley, southern Arizona. Photo courtesy Arizona -Sonora Desert Museum. Arizona. Photo by Mark Dimmitt. Al Morgan, photographer.

Representative cold- season therophyte: Cream - Representative facultatively chamaephytic Cups (Platystemon calffornicus) at Arboretum Pass therophyte: Desert Beardtongue (Penstemon parryi), between Arnett Canyon and Queen Creek Canyon, Boyce showing increased vigor over surrounding therophytes Thompson Southwestern Arboretum. Photo by Carol D. (Cryptantha, Lupinus), Pinal Pioneer Parkway, Arizona. Crosswhite. Photo by Carol D. Crosswhite. Crosswhite and Crosswhite Desert Life Forms 133

Scientists have been a long time in arriving at an under- ignore physiology and ecology (perhaps rightly so if the key is standing of the underlying factors relating to a life form classi- merely for identification purposes) that we tend to think of fication for desert plants. Is the fantastic shape of Ocotillo morphology alone as the reason why the organisms differ one (Fouquieria splendens) merely a random expression of physical from the other. Actually, the form or morphology is merely an structures which are theoretically possible or is it a unique life expression of function in nature. The present authors have form adapted to specific environmental factors -the specific devised a more or less phylogenetic classification of the higher form being tightly linked to function? Does Prickly Pear Cac- categories of the plant kingdom in the system of nature (see tus( Opuntia phaeacantha) just happen by chance to differ box) on the basis of modern concepts of form, function and markedly from Cholla Cactus (Opuntia bigelovii)? The present ecology which can be used as a starting point for a life form article attempts to show why the various life forms have their system. The present article deals only with Division 15 of the distinctive attributes. Admittedly, this is sometimes difficult plant kingdom (see box), the Spermatophyta or seed plants. or impossible owing to the fact that some crucial link with Within the Spermatophyta in our region we recognize 29 life specific environmental factors or physiological conditions has form categories, many of which bear little or no relationship to not yet been discovered. But the present authors have every units in a phylogenetic system. The geographic region covered confidence that in each case such a link does indeed exist and is that of the Sonoran Desert of southern Arizona, southern will some time be demonstrated. The life form concept is California, Baja California and Sonora, as treated by Cross - clearly at the heart of the question of how a plant actually white and Crosswhite (1982) in the Reference Handbook on functions in nature. the DesertsofNorth America. If an understanding of life forms is so important, why have scientists been slow to study them in detail? Probably several The Raunkiaer Classification factors are responsible. The very term for this science, "physi- of Seed Plant Life Forms. ognomy," has never been a name of high repute because it was The most widely used classification system for plant life originally used for the pseudo- science of predicting a person's forms is that developed by Raunkiaer (1905, 1934, 1937). criminal tendencies from analyzing his facial features. To Unfortunately for those who adhere to it in the Sonoran some, plant physiognomy is reminiscent of the medieval "doc- Desert, it was developed for use in a northern cold- temperate trine of signatures." Also, to many taxonomists a study of climate where environmental stress was chiefly due to winter environmental modification of plant form would smack of freezing weather. The Raunkiaer system places great emphasis Lamarckianism, one of the deadly professional sins. Accepting on the position of the buds or other perennating organs (tubers, polyphylesis as a common event would be another deadly sin. rhizomes, bulbs, seeds) in relation to protection from freezing "Wasting time" by studying phenotypic convergences which weather (Table 1). It preserves the time -honored separation of could possibly be non -genetic would be another such sin. (But trees, shrubs and herbs and to some extent makes accommo- most are indeed hereditary!) Surely every taxonomic scientist dation for the long recognized distinctions of hydrophytes has wanted his classifications to be monophyletic, truly phy- (water plants) and xerophytes (desert plants) from mesophytes logenetic. This may be due in part to a subconscious romanti- (normal plants). Its greatest deficiency is in the treatment of cism, of being a detective who someday might find the xerophytes. The only xerophytic category among the tradi- "missing link" in a particular taxonomic scheme. The phylo- tional major classes is that of plants with succulent stems. genist tends to see a phyletic drive or inherent force within the When Adamson (1939) and Cain (1950) used the Raunkiaer line being studied, -a force to account for the nature of the system for comparing vegetation in dry climates of the world divergences. The ecological reasons are less important for (see Table 2), they found little uniformity except in the high such a person, although it would generally be acknowledged incidence of therophytes (ephemerals or annuals). Cabrera that they must exist. On the other hand, the student of life (1955), faced with the necessity of treating life forms of plants forms sees every divergence as a possible convergence toward in Latin America, used a basic Raunkiaer system modified to other organisms living under similar environmental condi- include categories for Yucca, columnar cacti, cushion plants tions. In other words, the force driving the change is seen as and others. An up -to -date classification of desert plants of the external to the germplasm. Elsewhere in the world is there a world by the Raunkiaer system appeared in Deserts of the plant with the fantastic form of Ocotillo but unrelated phy- World (McGinnies, 1968). logenetically? If so, a comparison of the microhabitats and physiologies might reveal a commonality. Eureka! We have A Life Form Classification discovered the basis of the Ocotillo life form! For the Sonoran Desert Since life forms are not presented as phylogenetic units, Somewhat separate from the Raunkiaer system is a life form they need not be mutually exclusive. A plant could theoreti- classification scheme which has arisen from studies in the cally have the life form of a succulent and also the life form of a Sonoran Desert. This school of thought traces its roots back green- stemmed perennial. True, these could be combined to before Raunkiaer's publications to the pioneering observations form the category green- stemmed succulent perennial, but it by MacDougal (1903) in southern Arizona and northern would be easily recognized that several life form characteris- Mexico. He classified Sonoran Desert life forms on the basis of tics are combined in one plant. Thus, if we find no plant seasonal appearance and characteristics of stem and root, entirely like Ocotillo in some far distant desert, is there a plant recognizing such groups as ephemerals, perennials with en- which has some characteristic which we have previously seen larged roots or underground tubers, deciduous perennials, only in Ocotillo? Clearly by studying life form characteristics spiny perennials with tiny leaves, perennials with leaf protec- (such separate factors may be termed "physiognomic features ") tants (wax, resin, oil or varnish), succulent perennials and we have a powerful tool to shed light on the subject of plant halophytes (salt- tolerant plants). Shreve (1942, 1951) greatly strategies for survival. enlarged the system, recognizing 25 major life forms for plants Taxonomic keys to specific groups of organisms so often of the Sonoran Desert (Table 3). 134 Desert Plants 5 (4) Winter 1984

Crosswhite and Crosswhite (1982) modified the system, functional adaptation to the environment and in no way gave names to the life forms (Shreve had used only numbers) implies that individual plants have the ability to think or plan and provided preliminary explanations of the adaptations strategies. The "strategy" is characteristic of interaction of the involved, showing that each life form can be looked on as a life form with the environment over thousands of years and separate "strategy for survival" in the desert. The abundance of has been molded by repetitive occurrences, exigencies and life forms in the Sonoran Desert is looked at as promoting a stresses which must first be understood if one is to compre- separation of species activities to minimize competition and hend the nature of the strategic components inherent in the to make most effective use of scarce desert resources. For life form as we see it today. example, a shallow- rooted leaf succulent caudiciform such as Similarly, it should be understood that the concept ex- Century Plant (Agave shawii) may capitalize on light summer pressed earlier concerning partitioning of the environment by rains which would be of no use to a typical deep- rooted green - divergence of life forms in no way implies that plants stemmed microphyllous perennial such as Palo Verde (Cer- consciously make an effort to be polite, non -aggressive or cidium microphyllum). otherwise stay off the neighboring turf of other life forms. To It should be understood that in the sense used in this article, understand the mechanism of partitioning it is necessary to "strategy for survival" refers to a master plan of structural- examine the interplay of fitness vs. flexibility in the life forms

Authors' Outline of the Plant Kingdom in the System of Nature, Based on Modern Concepts of Form, Function and Ecology

A. Substances not organized into living material; the inorganic elles and mitosis or meiosis.... Phylum world World 1. GEOSPHERE (land, water, air) PROKARYOTA Division 4. CYANO- B. Non -living material composed of widely spaced molecules in PHYTA a gaseous sphere enveloping the land and ocean; air (blue -green algae) Sphere 1. ATMOSPHERE (air) II. Eukaryotic algae with plastids and other BB. Non -living material composed of closely spaced molecules in cell organelles as well as mitosis and a visible liquid or solid sphere interior to the atmosphere; meiosis Phylum EUKARYOTA land and water. (higher algae) C. Liquid water of the oceans, lakes, rivers, streams J. Unicellular eukaryotes Sphere 2. HYDROSPHERE (water) Subphylum PROTISTA CC. Solid stone and soil of the land Division 5. EUGLENOPHYTA Sphere 3. LITHOSPHERE (land) (euglenas) AA. Substances organized into living material; the organic world Division 6. XANTHOPHYTA (yellow - World 2. BIOSPHERE, (plants, viruses, animals) green algae) D. Living material lacking membrane systems Division 7. CHRYSOPHYTA (golden - Status 1. VIRUSAE (viruses) brown algae) DD. Living material with membrane systems Division 8. BACILLARIOPHYTA Status 2. ORGANISMAE (plants and animals) (diatoms) E. Organisms adapted to searching for and ingesting food Division 9. PYRROPHYTA Kingdom 1. ANIMALIA (animals) (dinoflagellates) EE. Organisms adapted to synthesizing food or to stationarily JI.Multicellular eukaryotes and unicellu- absorbing it; vegetable organisms Kingdom 2. lar forms which are very closely related PLANTAE (plants) Subphylum METAPHYTA E Plants not primarily adapted to covering land, not Division 10. CHLOROPHYTA having protective tissue enclosing reproductive cells; (green algae) plant body not differentiated into leaves, stems and Division 11. PHAEOPHYTA roots Subkingdom THALLOPHYTAE (brown algae) (simple plants) Division 12. RHODOPHYTA G. Thallophytes lacking chlorophyll -a; usually hete- (red algae) rotrophic or chemosynthetic but some photo- FE Plants adapted to covering the land (or some secondarily synthetic (but not oxygen -producing) by means otherwise), having protective tissue enclosing reproductive ofbacteriochlorophyll or "chlorobium chloro- cells; plant body usually differentiated into leaves, stems phyll." Superphylum MYCOPHYTA and roots. .... Subkingdom GEOPHYTAE (land plants) (bacteria and fungi) K. Land plants without vascular tissue H. Prokaryotic mycophytes without true chro- Phylum BRYOPHYTA Division 13. BRYO- mosomes but with circular DNA, without a PHYTA (mosses and liverworts) nuclear membrane, without mitochondria, KK. Land plants with vascular tissue ... Phylum without plastids, without Golgi bodies, with- TRACHEOPHYTA (vascular plants) out microtubules, without mitosis, without L. Vascular plants dispersing by means of meiosis Phylum BACTERIA (bacteria) spores Division 14. PTERIDO- Division 1. SCHIZOMYCOPHYTA PHYTA (ferns and relatives) HH. Eukaryotic mycophytes with true chromo- LL. Vascular plants dispersing by means of somes, with a nuclear membrane, with mito- seeds Division 15. SPERMA- chondria, with plastids, with Golgi bodies, TOPHYTA (seed plants) with microtubules, with mitosis, usually with M. Seeds naked Class GYMNO- meiosis Phylum FUNGI (fungi) SPERMAE (conifers and relatives) Division 2. EUMYCOPHYTA (true fungi) MM. Seeds enclosed in a fruit Class Division 3. MYXOMYCOPHYTA ANGIOSPERMAE (flowering plants) (slime molds) N. Plants with one cotyledon GG. Thallophytes with chlorophyll -a and capable Subclass MONO - of oxygen -producing photosynthesis COTYLEDONAE (monocots) Superphylum ALGAE (algae) NN. Plants with two cotyledons I. Prokaryotic algae of bacteria -like struc- ..Subclass DICOTYLEDONAE ture; lacking membrane -bound cell organ- (dicots) Crosswhite and Crosswhite Desert Life Forms 135

involved. Any species must have a degree of fitness for the tion, taking up its appreciation and study as a hobby. Many present environment while retaining a degree of flexibility to persons eventually grow a wide spectrum of the life forms and cope with future changes in the environment. As fitness sometimes use them in landscaping. If the vegetation of a increases flexibility decreases and vice versa, since one is typical north temperate region can be likened to a park or essentially the opposite of the other. garden, the vegetation of the Sonoran Desert at times can A life form with a high degree of flexibility is a generalist suggest a three -ring circus! rather than a specialist. Unfortunately for such a life form, the Indeed, the unique qualities and juxtapositions of desert life Sonoran Desert is extremely harsh, the environment and forms can be startling when seen the first time. To some people climate having multifaceted rigors. In such a situation a the landscapes never lose their alien exotic look. To some, the generalized life form might quickly perish. On the other hand, plant life forms seem to have animate or even sinister qualities a life form with a high degree of fitness for a particular niche or (cf. "Teddy Bear Cactus," "Jumping Cactus," etc.) and are insepar- microhabitat would likely survive. Thus, the specialist among ably thought of in association with Gila Monsters, Tarantulas, life forms narrowly adapts to a rigidly defined set of circum- Scorpions and Rattlesnakes. Perhaps it would not be too stances. By so doing, it leaves other niches and microhabitats difficult for a person to create a world of fantasy after exposing unpopulated. But whenever a particular niche or microhabitat one's self to the nurturing effects of Sonoran Desert landscapes is empty, there is the distinct possibility that some other with stark juxtapositions of strange life forms. In this regard it specialist life form will some day fill it. must be no accident that the creator of "Star Wars" grew up in Perhaps such a specialist might already exist 500 or 1,000 the Sonoran Desert where our sensors indicate the presence of miles away in a similar but not identical situation. If seed the 29 life forms which are discussed below! happened to be spread to the unused niche or microhabitat by strong winds, migrating birds or other dispersal mechanism, Cold- Season Therophytes The strategy of this life form is to exploit conditions which the life form might prove to have a degree of fitness for the new are seasonal and may not occur every year. These are the "here situation. Perhaps a particularly rigorous year might still kill many or all of the immigrants, but if the situation were today, gone tomorrow" spring annuals characteristic of spots in the Sonoran Desert with significant amounts of winter repeated often enough, a stable population of specialists might eventually arise having an increasingly higher degree of rainfall. Most have showy, even spectacular flowers in striking colors. The plants are usually not noticed until they flower, at fitness for the new home. which time the desert seems miraculously to spring to life. Through such processes the myriad of desert life forms have Such desert plants quickly became known in textbooks as apparently partitioned and repartitioned the resources of the "ephemerals" in allusion to Ephemera (Mayflies, the order Sonoran Desert, resulting in more efficient utilization. Under Ephemeroptera), the adults of which live only a few hours or less rigorous non -desert conditions where generalist life forms are successful there is much less proliferation of life forms. Thus, in the Sonoran Desert a particular life form may be Table 2. Spectra of Raunkiaer life forms in arid and subarid regions. restricted for many square miles to a single species such as Modified from Stanley Cain's (1950) review of life forms and phyto- Creosotebush (Larrea tridentate), whereas in a tropical rain climate. Symbols are explained in Table 1. forest a single square mile might contain 100 or more species Location of Survey Percent of Species per Life Form all having the same life form. In the Creosotebush example for S MM N Ch H GHH Th the Sonoran Desert, diversity is still likely to be present in the form of numerous other life forms. In such a situation the HOT DESERT number of plant species can be extremely high but with almost CLIMATES: unbelievable contrasts in form. Death Valley, California 3 2 21 7 18 2 5 42 This helps explain the enthusiasm with which visitors to 0 33 6 14* 0 47 the desert often become literally enchanted with the vegeta- Salton Sink, California 0 El Golea, Central Sahara 0 0 9 13 15 5 2 56 Table 1. Principal classes in the life form system of C. Raunkiaer Ghardaia, North Africa 0.3 0 3 16 20 3 0 58 (1905, 1934, 1937). Libyan Desert, N. Africa 0 3 9 21 20 4 1 42 Name Symbol Characteristics Oudjda Desert, N. Africa 0 0 0 4 17 6 0 73 Megaphanerophytes Mg Trees over 30 meters high Oudjda semidesert 0 0 0 59 14 0 0 27 }MM Mesophanerophytes Ms Trees 8 to 30 meters high Aden 0 7 26 27 19 3 0 17 Microphanerophytes Mi Shrubs or trees 2 to 8 meters high Ooldea, Australia 4 19 23 14 4 1 0 35 Nanophanerophytes N Shrubs under 2 meters high COOL DESERT CLIMATE: Chaemaephytes Ch Plants with buds or perennating points on the surface of the soil Transcaspian Lowlands 0 0 11 7 27 9 5 41 Hemicryptophytes H Plants with buds or perennating points within the top layer of soil HOT STEPPE CLIMATE: Tucson, Arizona 0 0 18 11 24* 0 47 Geophytes G Plants with bulbs, tubers or rhizomes Whitehill, South Africa 1 1 8 42 2 18 0 23

Therophytes Th Annuals Tombouctou, Mali 1 11 12 36 9 3 3 25 Marsh and water plants Helo- and Hydrophytes HH * At Salton Sink and Tucson, hemicryptophytes were not distinguished Stem succulents S Plants storing water above ground from geophytes. 136 Desert Plants 5 (4) Winter 1984 days, with larval stages typically lasting several years. Perhaps in response to precipitation from moist Pacific air masses the analogy is a good one because our ephemerals can literally which came into the desert with the west -to -east storm track spend many years as seeds hidden in the desert soil awaiting typical of the desert's cold season. They flower in February and rains heavy enough to break dormancy. March and generally mature seeds in late March or April. Such desert seeds are remarkably resistant to the harsh The geographic occurrence of this life form follows a precise factors of the environment and have amazing longevity. Our pattern defined by the overlap of favorable ranges of two cold -season "ephemerals" germinate with winter rain and must variables, 1 winter precipitation, and 2) soil temperature. complete their life cycles very quickly before the arid fore - There are regions in the Sonoran Desert which certainly have summer of May and June. The popular conception of them adequate soil warmth in winter for germination, but like the living only a few days, however, is a clear exaggeration. Chihuahuan Desert to the east, receive a preponderance of Actually, they spring up in November, December and January summer rain and little or none in winter. As could be expected,

Table 3. Life forms of the Sonoran Desert according to Shreve (1951(. The table is essentially the same as that published earlier by Shreve (1942) for all Southwestern deserts. The Sonoran Desert is the only American desert to have all of Shreve's 25 categories. Ephemerals: Strictly seasonal: Winter ephemerals 1.Daucus pusillus, Plantago fastigiata Summer ephemerals 2.Tidestromia lanuginosa, Pectis papposa Facultative perennials 3.Verbesina encelioides, Baileya multiradiata Perennials: Underground parts perennial: Perennial roots 4.Pentstemon Parryi, Anemone tuberosa Perennial bulbs 5.Hesperocallis undulata, Brodiaea capitata Shoot base and root crown perennial 6.Hilaria mutica, Aristida terni pes Shoots perennial: Shoot reduced (a caudex): Caudex short, entirely leafy: Leaves succulent 7.Agave Palmeri, Dudleya arizonica Leaves nonsucculent 8.Nolina microcarpa, Dasylirion Wheeleri Caudex long, leafy at top: Leaves entire, linear, semisucculent 9.Yucca baccara, Yucca brevifolia Leaves dissected, palmate, nonsucculent 10.Washingtonia filifera, Sabal uresana Shoot elongated: Plant succulent (soft): Leafless, stem succulent: Shoot unbranched 11.Ferocactus Wislizenii, Echinomastus erectocentrus Shoot branched: Shoot poorly branched: Plant erect and tall 12.Carnegiea gigantea, Pachycereus Pringlei Plant erect and low or semi -procumbent and low 13.Pedilanthus macrocarpus, Mammillaria microsperma Shoot richly branched: Stem segments cylindrical 14.Opuntia spinosior, Opuntia arbuscula Stem segments flattened 15.Opuntia Engelmannii, Opuntia santa -rita Leafy, stem not succulent 16.Talinum paniculatum, Sedum Wootoni Plant nonsucculent (woody): Shoots without leaves, stems green 17.Holacantha Emoryi, Canotia Holacantha Shoots with leaves: Low bushes, wood soft 18.Encelia farinosa, Franseria dumosa Shrubs and trees, wood hard: Leaves perennial 19.Simmondsia chinensis, Larrea tridentata Leaves deciduous: Leaves drought- deciduous: Stems specialized: Stems indurated on surface 20.Fouquieria splendens Stems enlarged at base 21.Idria columnaris, Bursera microphylla Stems normal: Stems not green 22.)atropha cardiophylla, Plumeria acutifolia Stems green 23.Cercidium microphyllum, Parkinsonia aculeata Leaves winter- deciduous: Leaves large 24.Populus Fremontii, Ipomoea arborescens Leaves small 25.Olneya tesota, Acacia Greggii Crosswhite and Crosswhite Desert Life Forms 137

such sites have a very poor development of cold- season thunderstorms. Since rainfall is biseasonal in much of the therophytes if at all. At the other end of the spectrum, where Sonoran Desert it is not unexpected that there should have winter precipitation is abundant but soil temperature a little developed a second set of "ephemerals" attuned to rains of the lower, the winter -active vegetation tends to be shrubby. With other season. Interestingly, the summer annuals are quite such lower soil temperatures, germination of winter annuals is different from the winter ones. Indeed, they usually even poor or non -existent, only well -established plants with deep belong to quite separate taxonomic families. The two driest root systems being able to take advantage of clear sunny days. months of the year, May and June, intervene between the two Cold- season therophytes thrive in the Arizona Upland divi- sets of therophytes. sion of the Sonoran Desert, the Lower Colorado -Gila division, The hot -season therophytes occur generally only in regions the Sonoran Plains division, northern Baja California, the heavily influenced by the Sonoran Monsoon. Four of the Mojave Desert of California and the Coastal Sage Scrub of that seven divisions of Sonoran Desert fit into this category: the state. The life form exploits conditions which are present only Sonoran Foothills, Sonoran Plains, Central Coast, and Arizona a few inches either side of the interface of atmosphere with Upland. Much of the moisture for the Sonoran Monsoon soil. The brief life span makes it almost certain that the plants originates in the Gulf of Mexico rather than the Pacific. Rains will be small. Both roots and shoots typically are short. from this source also fall in the Chihuahuan Desert, a region It is a well -established fact that there are good years and bad (as opposed to the Mojave Desert) of summer rather than years for spring wildflowers in these regions. The governing winter precipitation. factor is the position of the jet stream. During any particular Shreve (1951( has shown that the summer annuals of the winter the flow of air in the upper atmosphere tends to create a Sonoran Desert are similar to or identical with summer - pattern which is more apt to remain the same than to change. rainfall plants of the Chihuahuan Desert or western Texas. During winters when the storm track is latitudinally high, the The relatively high temperatures of summer allow the plants Pacific Northwest receives rain that might have fallen further to develop thick stems, extensive branches and many leaves. south. Under such conditions the desert will tend to be rather Such rank growth contrasts sharply with the delicate appear- drab. During years when the track is to the south, rain may fall ance of the cold- season therophytes. The hot -season thero- abundantly in the Chaparral of southern California and phytes often have rather weedy characteristics. The Papago, central Arizona and in the Mojave Desert and northern endemic agriculturists of the Sonoran Desert, seem to have portion of the Sonoran Desert. These are the banner years of learned enough about the Sonoran Monsoon and the response desert splendor when whole hillsides take on a bright orange of hot -season therophytes to enhance, control and modify it hue, vivid purple or other color from mass displays of for production of food through thunderstorm agriculture. coordinated blooming. Some hot -season therophytes of the Sonoran Desert are Occasionally there is a rare year when winter soil moisture Spurge or Golondrina (Euphorbia albomarginata), Devil's Claw and temperature are so optimum that plants normally thought or Unicorn Plant (Proboscidea), Jimson Weed (Datura), Summer to be rare (or in one or two instances, nearly extinct) have Poppy (Kallstroemia), and members of the Four O'Clock Family amazed botanists by appearing in large quantities. In one well - such as Allionia and Boerhaavia. documented case a rare plant, thought to be virtually extinct, suddenly filled an entire valley. Facultatively Chamaephytic Therophytes A mature cold- season therophyte seems to show no struc- Some desert plants may live as therophytes but under tural adaptations to desert conditions. Many authors have favorable conditions might persist for two or three years. They claimed that the "ephemeral" life form is not a true desert one, adapt to drought by becoming more or less dormant. If drought but rather a drought- avoiding strategy whereby the plants are is severe they die like therophytes, but seed produced earlier able to live under temporary non -desert conditions. This will germinate in a later season. It is obvious that the strategy seems a little short -sighted, however, since there are major of this life form is to capitalize on the same environmental adaptations in the seeds to render them viable over extremely conditions exploited by true therophytes but with the advan- long periods of time under harsh desert conditions. Resistance tage of having a good headstart if and when environmental to germination ensures that it will not occur unless truly conditions permit. heavy rainfall occurs. Such resistance results from a relatively For facultatively chamaephytic therophytes to survive it is impervious seed coat or from the presence of chemical necessary for them to set seed in synchrony with competing inhibitors which must be thoroughly washed away from the " ephemerals" since there can be no guarantee that they will seed coats. The mature plant of the life form usually has a survive the dry period any better than normal therophytes. delicate, wispy appearance resulting from the rapid growth Opportunism is the key to the survival strategy of this life rate which was necessary to exploit seasonal moisture. form. By having a headstart such plants could become larger Since the winter annuals of the Sonoran Desert are exposed and react with the environment more vigorously. In theory to conditions which can suddenly turn relatively cool (or even they would have more time for photosynthesis resulting in cold) itis perhaps not surprising that they show strong more energy for producing seed, perhaps in increased numbers relationships with the plants of the Mojave Desert, a cool - and with superior vigor. The plants that persist from one year winter region. Cold- season therophytes in the Sonoran Desert to the next, however, tend to carry over diseases and pests that include Fiddleneck (Amsinckia intermedia), Nievetas (Cryp- have a headstart too, decreasing the actual advantage over the tantha(, Scorpion -Tail (Phacelia), California Poppy (Eschscholt- therophyte. An analysis of the pros and cons of the therophytic zia), Indian Wheat (Plantago), and Blue- Bonnet (Lupinus). condition and that of the facultative chamaephyte is exactly equivalent to the debate by agriculturists over the advantages Hot -Season Therophytes of a stub -crop over a seed crop. For example, farmers may cut The strategy of this life form is to exploit brief summer cotton back to stubs rather than plowing the plants under and Representative tuberous geophyte: Bottle -Root The "Ajo Lily" (Hesperocallis undulata) is an edible bulb Gourd -Vine (Maximowiczia sonorae) west of San Ignacio, geophyte. Whether it gave rise to the name for Ajo, Arizona Baja California del Sur. Photo by Kent Newland. has been much debated. Vic Housholder.

re- seeding the next year. resting in the soil until favorable conditions return. New plants may grow faster from the stubs and give a better The bulb geophytes of the Sonoran Desert have a mono - crop under some circumstances. But if numerous insects have podial scapose growth habit and are all of small or moderate overwintered on the stubs, not only may the stubcrop be stature. In contrast to the root geophytes, none climb over damaged when it grows out, but even crops of other farmers other vegetation or proliferate by spreading over the ground. who started with fresh seed. For such reasons, stub -cropping The above -ground plants tend to be narrow and to rise up has sometimes been made illegal. Diseases and pests of through other small life forms, stones or leaf litter toward facultatively chamaephytic therophytes may present a greater sunlight. Generally bulb geophytes grow in places where large problem than diseases and pests of true perennials. Although perennial plants are at a disadvantage- sandy, thin -soil areas perennials might generally be supposed to harbor pests from which have only small grasses and herbs and are relatively one year to the next, they do not have to produce a large open, the competition chiefly being with annual species. amount of new biomass or new stand of individuals each year The life form draws on energy stored in the bulb to achieve a and can perhaps reach a stable equilibrium with the attacking headstart over "ephemeral" therophytes. This competitive organisms better than can the typical facultative chamaephyte. advantage presents the same problem as that with the root That facultatively chamaephytic therophytes may have geophyte, namely that the above -ground habitat can be little actual advantage over therophytes or chamaephytes is usurped by other perennial vegetation after the plant season- suggested by the relative paucity of species which can be classi- ally dies back to its perennating organ. As a result, in the fied under the life form. Some species respond to both summer Sonoran Desert the life form seems to be effective only where and winter rain, such as Desert Mallow (Sphaeralcea), Crown - soils are relatively poor and incapable of supporting other life beard (Verbesina encelioides) and Desert Marigold (Baileya forms in the stressful season. multiradiata). Others may respond basically to summer rain Bulb geophytes are common outside of the desert in grass- only (Aplopappus) or winter rain only (Penstemon parryi). lands (note the absence of woody perennials!) or in deciduous forests where woody perennials are leafless and dormant during the season when bulb plants are active and flowering. Bulb Geophytes Since grasses are rarely dominant features of Sonoran Desert Bulbs are underground perennating organs consisting of a vegetation and there is frequently a preponderance of non- dormant meristem surrounded by fleshy protective leaves. deciduous (evergreen) woody perennials, it is not surprising They function similarly to the buds of woody plants from that there are few species of bulb geophytes. All those which which each new year's growth bursts forth. In contrast to the are known respond to our winter precipitation. None has yet situation seen in a typical tree or shrub, the bud is protected been identified which responds to summer rain. Examples of from the harsh environment of the unfavorable season by thislife form in the Sonoran Desert are Mariposa Lily (Calochortus), Wild Onion (Al lium), Desert Lily (Hesperocallis undulata), and Covena or Blue Dicks (Brodiaea pulchella). Tuberous ("Root") Geophytes This life form consists of plants with underground peren- nating organs other than bulbs. Each year new stems arise from an underground rhizome or from a root -stock having under- ground stem tissue associated with a huge root. The survival strategy is similar to that of the therophyte in avoiding dry periods or cold periods. In the case of the geophyte the above- ground parts of the plant completely die after seasonally favorable conditions have ended. According to Shreve (1951) the Sonoran Desert has no root geophyte which responds to both summer and winter precipitation, although the reason for this is not known. The striking phenomenon relating to our root geophytes is that many (particularly those with the most massive and long -lived perennating organs) tend to be vines or spreading plants with flexuous stems. But what mechanism could cause a linkage between tendencies for large underground structures and above- ground vining stems? Although we have found nothing in the literature pertaining to this subject, we advance the following explanation. Root geophytes take advantage of the desert's most favorable habitats (often riparian) with above average soil texture, depth, moisture and minerals. Once having invaded such a site through seed dispersal, the root geophyte must come to grips with competitive pressures from other life forms which had already become established there. In most such instances the seedling root geophyte would probably not survive. But given Representative hemicryptophytic grass: enough time, habitat openings would occasionally result from Fountain Grass (Pennisetum setaceum) in propagation at fire, flooding or other phenomena and the life form would the Boyce Thompson Southwestern Arboretum. This eventually become established. In contrast to the desert introduced ornamental self -seeds in parts of the Sonoran therophyte where year -to -year re- establishment requires dis- Desert and is now an established member of the flora. persal of huge numbers of seeds to open environments, there is Photo by Frank S. Crosswhite. selection in the root geophyte for non -dispersal. Once having become established in a favorable habitat, the strategy of the root geophyte is to hold the habitat for a very long period of time. The establishment of large underground perennating drought very effectively through the further adaptation of organs allows the life form to keep its foothold, but at a having succulent leaves. tremendous expense. Other examples of root geophytes, arranged roughly in order The big disadvantage is that the root geophyte must occupy of decreasing massiveness of underground structures and the one spot on earth where its perennating organ lies. When decreasing flexuosity or vining nature of stems, are Wild the root geophyte dies back for the year it is likely that its Desert Cucumber (Marah gilensis), Bottle -Root Gourd -Vine above -ground habitat will be usurped by trees, shrubs or other (Maximowiczia sonorae), Buffalo Gourd and Coyote Melon plants -the surrounding vegetation. In such favorable habitats ( Cucurbita foetidissima and C. digitata), Maravilla (Mirabilis where soil is good and deep (often riparian) with above average multiflora), Desert Larkspur (Delphinium scaposum), and moisture, openings in the habitat quickly fill in. Taller plants Desert Anemone (Anemone tuberosa). shade out the smaller ones. But our successful root geophytes, by vining or otherwise spreading, turn the table on the Hemicryptophytic Grasses competition, successfully proliferating toward the light and Grasses are very successful in the Upper Sonoran Life Zone encroaching on or growing over the other vegetation! Indeed, but much less so in the Sonoran Desert itself (all of which lies the presence of the other vegetation improves the leaf litter in the Lower Sonoran Life Zone). Perhaps this is due to the and enriches the soil to the benefit of the root geophyte. It also generally hemicryptophytic nature of grasses whereby as provides a rigid woody framework for elevating and effectively Shreve (1951) indicated, the "inner basal part of the cluster of displaying leaves of the root geophyte to the sun. Since the life shoots and leaves and the upper part of the root system persist form dies back to the underground perennating organ each under ordinary unfavorable conditions." Exceptions which year, it could not achieve such a woody framework on its own. seem extremely well- adapted in parts of the Sonoran Desert In the Sonoran Desert the annual dieback usually is a include grasses which actually belong to other life forms. For response to drought. But due to cold air drainage (the good soils example, Brown Brome Grass (Bromus rubens) is in actuality a are usually in low spots or along streams) the habitat may be cold- season therophyte and Big Galleta Grass (Hilaria rigida) cold enough in winter for some species to die back then. Some which roots at the nodes and very effectively stabilizes sand plants in the winter die -back category are facultative ever- dunes, actually has the life form of a perennial shrub. greens when winters are mild. One such example, Desert True rangeland, where grasses perennate from the base after Grape Ivy (Cissus trifoliata) copes with summer heat and having seasonally died back or been grazed by domestic or 140 Desert Plants 5 (4) Winter 1984 native mammals, is not really common in the Sonoran Desert. tissues in summer can experience a critical heat build -up in Only in the upper elevational reaches of this desert, and in the hotter regions of the desert. At the other extreme, high broad transition where oak woodland or chaparral gives way to moisture content of the leaves can make the life form actual desert, do the truly hemicryptophytic grasses become sensitive in the winter to freezing in colder regions. dominant components of the vegetation. Examples of leaf succulent caudiciforms are Hen -and- Grasses typically have fibrous roots limited to the top few Chicks (Dudleya and Graptopetalum) and Century Plant inches of soil and must become dormant when this near - (Agave). The latter genus has been extremely successful in surface soil layer dries out. The poor success of hemicrypto- adaptively radiating into numerous habitats, effectively coun- phytic grasses in our desert seems due to the extreme nature of tering hazards relating to heat load and freezing. heat and desiccation in this layer and the likelihood that during most years the length of time that dormancy can be Leaf Semisucculent Caudiciforms maintained will be exceeded. In the Sonoran Desert this life form seems to be confined to Plants of this life form seem to undergo vegetative growth Yucca, floristically a relatively important genus including any time of the year when soil moisture is favorable, although such well -known plants as Spanish Dagger (Yucca baccata), flowering tends to occur in the summer, at least in the north. Palmilla (Yucca elata), Datilillo (Yucca valida), and Joshua Tree The strategy for survival of the hemicryptophytic grass has (Yucca brevi f olia ). Species differ in leaf succulence and size and been likened to that in the life form of the bulb geophyte but in woodiness of trunk. All species are decidedly less succulent with smaller, multiple sites of perennation. Indeed many than Agave, tend to be more resistant to freezing, and have less scientists classify grasses with fleshy underground peren- wax on the leaves. nating organs as true geophytes. Hemicryptophytic grasses of The leaves are characteristically shorter and narrower than the Sonoran Desert include Sacaton Grass (Sporobolus those of Agave and seem to be of less value in condensing wrightii), Salt Grass ( Distichlis spicata), Tobosa Grass (Hilaria atmospheric moisture. They differ from Agave also in rarely mutica), Tanglehead Grass (Heteropogon contortus), and Blue - forming simple rosettes. Adventitious roots may form on stem (Bothriochloa barbinodis). trunks covered by old leaf bases. Such roots absorb water which has soaked into fibers of the old leaves. Such a Leaf Succulent Caudiciforms phenomenon also occurs in palms. As in other succulents, this life form is based on crassula- Yucca, in contrast to Agave, has a deep and rather massive cean acid metabolism. The plants are generally rooted in the root system which can exploit water which has been stored in same surface layer of soil as the hemicryptophytic grasses but the ground through much of the spring and summer but which store water in succulent tissue from time of plenty to time of resulted from precipitation in winter. The strategy of the leaf scarcity. Evapotranspiration is reduced by the thick waxy semisucculent caudiciform is to exercise extreme frugality in covering of the epidermis and the opening of stomata only at using moisture reserves of intermediate and deep soils in night. Although photosynthesis in typical plants requires combination with those of the semisucculent leaves, trunk diurnal stomatal gas exchange, the crassulacean metabolic and roots, taking advantage of crassulacean acid metabolism pathway results in carbon gain (increasing with coolness) and diurnal sealing of internal tissues from the environment. when the organic acids of the succulent tissues are chemically Yucca grows rather slowly. The "permanent" evergreen leaves upgraded by combining with carbon dioxide entering while are re -used for many years, reducing the need to produce new the stomata are temporarily open at night. During the day the biomass. Shreve (1951) treated this life form as intermediate process is reversed and the acids yield carbon dioxide back up between the typical leafy tree and the columnar cactus, to be combined with stored water in the presence of sunlight noting that the "photosynthetic and transpiring surfaces are for photosynthesis to occur. limited to the leaves, but are fixed in area so as to admit of no In the leaf succulent caudiciform, succulent leaves are seasonal reduction." massed together as a rosette on a caudex consisting of a compact, short (sometimes hidden) stem. An extensive but Narrow -Leaf Nonsucculent Caudiciforms shallow root system harvests water from light rains (which This life form is related to that of Yucca but is characterized would usually evaporate quickly and be lost to the desert) or by the presence of grass -like or ribbon -like leaves which, even from condensation of dew. The waxy covering on the although very fibrous, thick and tough, can scarcely be des- succulent leaves not only seals the moist inner tissues from cribed as truly succulent. The plants seem to have the life form the environment but permits condensation of dew or drizzle of a grass combined with extremely xeromorphic evergreen into balls of water which roll down the rosette of leaves to soak leaves and a well -developed caudex or "heart" similar to that of into the soil directly under the plant where a mat of roots is Yucca or Agave. The leaf rosettes may spring directly from the extremely efficient at intercepting the water. The leaves of the ground or may be displayed atop heavy trunks, rendering the rosette typically radiate out and upward in all directions to plants somewhat palm -like in appearance. intercept moisture, converging below at the caudex. They Narrow -leaf nonsucculent caudiciforms occur in eastern frequently are curved on their upper surfaces to form channels and northern regions of the Sonoran Desert, often on north - which contain the moisture flow in continuous streams down facing slopes, where rainfall is relatively high, evapotrans- to the root mat. piration relatively low, and temperatures lower than average. Although this life form has several clear competitive They are particularly common in the region of overlap of advantages under Sonoran Desert conditions, there are some desert with either grassland, oak woodland or chaparral. distinct disadvantages. The waxier the leaf surface, the more Examples of this life form are Beargrass (Nolina), Sotol likely are the sun's rays to be concentrated to burn the (Dasylirion) and False -Yucca (Hesperaloe), all related taxo- epidermis and harm the underlying chlorophyll. Without the nomically to Agave and Yucca. However, if a member of the cooling effects of evapotranspiration, the internal succulent grass family were to have sharp- edged, tough evergreen leaves Representative leaf succulent caudiciform: Murphey s Century Plant (Agave murpheyi) growing at the Boyce Thompson Southwestern Arboretum. Photo by Fred Gibson.

Representative narrow -leaf nonsucculent caudiciform: Beargrass Tree (Nolina palmeri) at Yubay, Baja California del Norte. Representative semisucculent caudiciform: Spanish Dagger (Yucca treculeana) cultivated at the Boyce Thompson Southwestern Arboretum. For comparison a narrow -leaf nonsucculent caudiciform is in the foreground and a leaf succulent caudiciform in the right foreground. Representative broad -leaf nonsucculent caudi- ciform: Desert Fan Palm (Washingtonia robusta) at Cata- viñá, Baja California del Norte. Photo by Kent Newland. 144 Desert Plants 5 (4) Winter 1984

Representative leaf succulent noncaudiciform: Salt Purslane (Sesuvium verrucosum) at San Ignacio Lagoon, Baja California del Sur. Photo by Kent Newland. which resisted grazing animals, it would fall at about this point the surface of the soil and to hold onto the habitat by sheer in the life form classification. dominance in size and height. The habitat used by this life form is the most favorable one in the desert -a virtual oasis Broad -Leaf Nonsucculent Caudiciforms where the water supply is dependable and freezing weather is The true palms fall into this category. The life form is non -existent or rare. There are important adaptations which characteristic of the tropics. In the Sonoran Desert, as opposed allow the life form to monopolize such favorable sites. to the narrow -leaf nonsucculent caudiciforms, it is restricted Perhaps most important is the vigorous monopodial type of to sites where winter freezing is least probable. Growth is growth which channels new biomass into a single towering monopodial (unbranching). Only arborescent species occur in pole enabling the leaves to attain an exaggerated elevation the Sonoran Desert. Rosettes of large, coarse, tough, sharp - above the ground, rising above all competing vegetation to edged, compound (branched) leaves occur at the tops of tall ensure that interception of energy from the sun will be cylindrical stems. Although fibrous tissues of the stem may permanent. Second, the leaves are massively broadened, hold some moisture for emergency use, the life form is divided, strengthened with fibers and elongated to increase the decidedly non- succulent. surface area and arranged in an umbrella -like rosette which Plants in this category are found only where water is rather increases the amount of light intercepted and ensures a permanently available at shallow depth. This restricts the maximum "shading out" effect on competing vegetation. plants to drainage channels, canyon bottoms, or where water Examples of this life form in the Sonoran Desert are the seeps from springs or aquifers. Sometimes such locations Arizona- California Fan Palm (Washingtonia f ili f era ), Mexican appear rather arid if water use by the palms is in equilibrium Fan Palm (W robusta), Palma Ceniza (Brahea armata), Palma de with the quantity made available by the seep or other water Taco (B. brandegeei), and Brahea roezlii. Exotic species which source. The roots make a dense but shallow mat directly under have gone wild in Mexican portions of the desert, primarily the trunk. Even the lower portions of the trunk often develop a Baja California, are Date Palm or Datil (Phoenix dactylifera) thick covering of adventitious roots which apparently inter- and Coconut Palm or Cocotera (Cocos nuci f era). cept water which runs down the trunk, soaks into old leaf bases, or pools up on the ground. Leaf Succulent Noncaudiciforms The survival strategy of this life form in the Sonoran Desert In the Sonoran Desert these are small, rather soft, shallow- is to monopolize water which is present through the year near rooted plants. They contrast markedly with the coarse, tough Crosswhite and Crosswhite Desert Life Forms 145 caudiciforms. Some are even annuals. Although the leaves do store enough water to avoid wilting during short drought periods, the plants apparently do not have enough succulent tissues to survive during protracted drought in more xeric regions of the desert. Since leaves are generally not arranged in rosettes, there is not the significant condensation and fun- neling of atmospheric moisture to the base of the plant that characterizes the typical leaf succulent caudiciform. The leaf succulent noncaudiciforms of the Sonoran Desert have the survival strategy of competing with other small shallow- rooted plants for water, but surviving stress of periodic drought by drawing on moisture reserves in the succulent leaves. Degree of succulence varies greatly but apparently all species are capable of crassulacean acid metabolism. Sonoran Desert examples of this life form are Stylophyllum attenuatum in the Crassulaceae family, Nitrophila occidentalis in the Chenopodiaceae family and members of the Portulacaceae family such as Purslane (Portulaca), Rock Purslane (Calan- drinia), Talinum and Calyptridium.

Monopodial Stem Succulents This is one of the most successful and characteristic life forms of the Sonoran Desert. The plants have unbranched barrel- shaped bodies containing very large quantities of suc- culent water -storing tissue. The popular conception of such plants as virtual barrels of water on the desert is perhaps a good one. They are like a conservative banker with a vault full of money during an economic depression. Perhaps the striking feature of this life form is its ability to remain conservative while actually having a firm grip on a large amount of surrounding habitat. This is achieved by having 1) a massive but shallow root system which radiates great distances from the plant to intercept and absorb moisture from even light rains, 2) a vault -like water -storing plant body with the greatest volume -to- surface ratio possible, 3) a waxy impermeable epidermis and crassulacean acid metabolism, 4) an absence of leaves, photosynthesis occuring in the highly protected stem, 5) extremely slow, often imperceptible plant growth which minimizes energy demand and production of photosynthate, 6) lowering the amount of energy and water used in reproduction, the fruits lacking a sweet, moist pulp (in contrast to ones of other cacti such as Saguaro, Prickly Pear or Pincushion), and 7) by growing in rather poor locations which Representative monopodial stem succulent: have long periods between rains, where plant cover is low and Golden Compass Barrel (Ferocactus acanthodes var, competition of little significance. eastwoodiae) at the Boyce Thompson Souhtwestern Although the monopodial stem succulent seems extremely Arboretum. Photo by Carol D. Crosswhite. well- adapted to the desert, it has a serious drawback. It is possible for large animals to break into the plant body to "steal" the stored water. This is a severe problem for this particular including such species as Compass Barrel (F. acanthodes), Fish- life form because it has a single unbranched water -storing hook Barrel (F.wislizenii), Fire Barrel (F. gracilis), Golden - organ, whereas other succulent life forms have multiple such Spined Barrel (F chrysacanthus), and Ferocactus covillei. organs or ones divided into parts so that loss of one or a part may not seriously affect the organism. But once the single Arborescent Oligopodial Stem Succulents organ of the monopodial stem succulent is ruptured, desic- This is the life form of the giant Saguaro Cactus (Carnegiea cation will occur. Rot is also likely to set in. The plant will gigantea) of Arizona and other large columnar cacti of Sonora have a high likelihood of dying unless it can form a layer of and Baja California, particularly Cardón Pelón (Pachycereus protective callus tissue to restore the integrity of the stem. In pringlei) and Haircomb Cactus or Cardón Hecho ( Pachycereus the Sonoran Desert all monopodial stem succulents have pecten- aboriginum). Although this life form stores water and numerous sharp treacherous needlelike spines (often curved shares many of the adaptive features of the typical monopodial like fish -hooks) which afford some protection from animals. stem succulent, it goes much further in adaptive strategy. In the Sonoran Desert this life form is represented by the The most striking feature of the life form is that plants act various species of Barrel Cacti in the genus Ferocactus, very differently (almost schizophrenically) during different phases of their life. We base the following analysis on our study of the Saguaro. Life of a representative plant can be divided into three phases, 1) a conservative phase of 25 -35 years rather reminiscent of the life of a typical monopodial stem succulent, 2) a reaching -out or emerging phase of 35 -45 years somewhat analogous to the period of trunk formation in a palm, and 3) an exploitive phase of 50 -100 (or even more) additional years. Newly germinated Saguaros seem almost like little bags of water. They will surely die if exposed to the full effect of the sun's rays in summer or freezing in winter. Success of a young plant depends on the presence of a "nurse tree" such as Palo Verde (Cercidium) to shelter it from sun and frost. The leaf litter, enriched soil, higher relative humidity and less fluctu- ation in temperature under such a tree makes a good site for Saguaro germination. Seeds of this life form are less apt to germinate in other locations and will probably die during the first year from sun or frost if they do. A Sonoran Desert site which has proven successful in sustaining a tree such as Palo Verde will automatically be one with very favorable characteristics of soil moisture and texture. During the conservative phase of its life, a typical Saguaro appears to be a good guest under the nurse tree, growing slowly and using only a minimum of resources. But an immense root system is spreading far and wide underground, creating a foundation seemingly out of proportion to the needs of such a moderate -sized plant. As the plant matures, it becomes less sensitive to freezing and generally is injured by sun only on surfaces which have been over -shaded or if the plant is severely dehydrated. After 25 or more years, when the root system has matured, the guest plant suddenly loses much of its conservative nature, beginning to metabolize at a much higher rate and growing much faster. During this phase of life it rises up through the branches of the nurse tree and emerges into direct sunlight, achieving a height of 8 -15 feet or more. By the time such a height is achieved the Palo Verde or other tree usually becomes water stressed because of the efficiency at which the root mat of the Saguaro intercepts moisture which would otherwise have been available to the tree. The site, with soil moisture favorable enough to have nourished the tree to maturity, is about to fall to the exclusive use of the tree's unwanted guest. As the tree becomes senescent, the Saguaro begins oligopodial growth - branching occurs and numerous parallel trunks rise up to increase the photosynthetic ability of the plant. As the Saguaro grows, eventually the nurse -plant dies as a result of competition with the cactus. Production and growth of parallel branches continues for a number of years until an equilibrium has been reached where all available soil moisture is being exploited. Among mature Saguaros, massiveness appears to be an indicator of quantity of exploitable soil moisture at a particular site. The supposition that this life form uses very little water was negated by Blumer (1909), who studied an exceptionally huge and vigorous Saguaro in a moist and nutrient -rich situation near a stock tank. The life form produces the most massive plants of the entire Sonoran Desert. A mature Saguaro can weigh many tons. When it finally dies, a new Palo Verde or other tree will probably soon germinate at the nutrient -enriched site where the cactus decomposed, and the approximately 200 -year cycle begins again. Representative arborescent oligopodial stem Clustering Stem Succulents succulent: Saguaro (Carnegiea gigantea) at the Boyce The survival strategy of this life form is similar to that of the Thompson Southwestern Arboretum. monopodial stem succulent but modified for increase in sur- face area in proportion to volume, to increase photosynthetic potential. The increased photosynthetic area permits a higher metabolic rate and more active growth which can respond to a year or series of years with above average conditions. In contrast to the conservative nature of the typical monopodial stem succulent, many clustering stem succulents produce juicy fruits with high sugar content in order to achieve wide dispersal by animals. This life form retains considerable flexibility. Although spread to new sites by seed is commonplace, spread of individual plants to adjacent space through clustering is also characteristic. Adventitious roots may form at the base of branches to increase the number of roots under a clump. In the Senita Cactus (Lophocereus schottii) aerial roots even occur at the bottoms of higher branches. If such branches break off during violent storms, or plants fall over, the roots grow quickly into the soil. This is perhaps the extreme development of a basic adaptation of clustering stem succulents to push outward from the original site of germination to enlarge the living space and press competing vegetation aside. Another advantage of clustering is that a stem rosette often forms which can function like the leaf rosette of caudiciform plants to intercept rain, dew or drizzle and conduct it to the central point under the plant. Examples of clustering stem succulents in the Sonoran Desert are Hedgehog Cacti (Echinocereus), Pincushion Cacti (Mammillaria), Organ Pipe (Stenocereus thurberi), Senita (Lo- phocereus schottii), and Red -Bird or Slipper Plant (Pedilanthus macrocarpus) of the Euphorbiaceae family. Decumbent Creeping Stem Succulents This is a rather unique life form of mobile terrestrial rooted plants. The plants lie on the ground with the heads pointing upward. The body sends new adventitious roots into the soil as Representative clustering stem succulent: the individual moves along the surface. As the head advances Organ Pipe (Stenocereus thurberi). In this photo Frank S. across the sandy plain the tail dies. In this manner a plant may Crosswhite pauses with a cold Cerveza Tecate on a hot move a considerable distance over a period of time. Since new day in June, 1960 during a botanical survey of Sonora and body material is constantly produced at the head there is no the Gulf Coast. theoretic reason why an individual could not live forever. Given enough time, a swarm of plants would have gravitated Branching can be quite rambling or octopus -like, the branches to the microhabitats most conducive to survival. rooting into the soil when they touch the ground, even though In the Sonoran Desert this fascinating life form is repre- remaining attached to the main plant body. sented by the Creeping Devil (Machaerocereus eruca), also Generally the species have spines which cling to the fur or known as "Caterpiller Cactus." Its closest relative is an erect flesh of large animals so that segments are dispersed to new cactus which would be classed as a cylindrocaulescent shrubby growing sites. Some species have fruits which remain green, stem succulent. The decumbent creeping species has much fall from the plant, take root, and grow new adventitious stems wider spines. Since the prostrate nature renders the creeping from the ovary wall! In the typical cylindrocaulescent shrubby species more susceptible to solar burn on clear days (because stem succulent any new vegetative growth represents poten- at right angles to the sun's rays), the shading of the plant body tial reproduction because any branch has the capability of by the wider spines is beneficial. These tough, stout spines becoming a free -standing plant. Through this mechanism of also provide protection from biting and chewing animals clonal reproduction the species tend to become colonial which crawl along the ground. perennials with the colony radiating out from the original site of introduction. Cylindrocaulescent Shrubby Stem Succulents The life form clearly foregoes genetic flexibility (character- Stems of this life form are cylindrical, narrow, elongate and istic of sexual reproduction) in favor of temporary environ- much -branched. The ramification of photosynthetic stems mental fitness passed on through clonal reproduction. This and the presence of a vigorous root system allow more rapid would present a severe problem to a species if its particular growth than in more conservative cacti. The survival strategy habitat or any significant accompanying environmental is related to that of the clustering stem succulents, but with factors were to change. Although members of the life form exaggerated proliferation of photosynthetic stem area by often produce few or sterile, inviable seeds, a degree of means of octopus -like growth or radiating branches. Repro- flexibility is kept by species or segments thereof (populations) duction by seed becomes less common in the life form and is retaining the capability of setting viable seeds. rare or virtually absent in some species. Fragmentation of the Sonoran Desert examples of the life form are the numerous stem is common, each segment having the capability of pro- "Cholla" cacti (Opuntia subgenus Cylindropuntia) such as ducing adventitious roots and growing as a new individual. Chain -Fruit (O. fulgida), Teddy -Bear or Jumping Cactus (O. Representative decumbent creeping stem succulent: "Creeping Devil" or Caterpillar Cactus (Machaerocereus eruca) at Pozo Grande, Baja California del Sur. Photo by Mark Dimmitt.

bigelovii), Pencil Cholla ( O. arbuscula), Desert Christmas to mid -afternoon. Cactus (O. Ieptocaulis) and many others, as well as Octopus The Beavertail Cactus (Opuntia basilaris), which grows only Cactus (Rathbunia) in Sonora and Machaerocereus gummosus in cooler locations, has relatively few but elongated pads in Baja California. which rise directly from the ground. Being broad at the top but narrow at the base, each pad has a degree of flexibility or curl Platycaulescent Shrubby Stem Succulents which resembles somewhat the dish of a microwave antenna! This life form differs from the prior cylindrocaulescent This comes the closest to an ability for "solar- tracking" of any category only in having flat rather than cylindrical stems. The Opuntia species we have yet studied. These solar receptors Sonoran Desert examples are extremely close taxonomically warm the plants up and allow them to "come to life" quickly on to species in the cylindrocaulescent category, all being in the a winter morning and begin to photosynthesize! "Prickly Pear" division (subgenus Platyopuntia) of Opuntia, Just as flat succulent stems displayed at right angles to the the same genus mentioned prominently under the cylindro- sun's rays become extra warm in the daytime, they very caulescent category. Nevertheless, the interaction by this life effectively radiate heat away at night. Far from being a form with the environment is quite unique. disadvantage, this actually maximizes carbon -gain at night. The flat stems develop a much greater heat load than do the The chemical union of carbon dioxide with organic acids takes cylindrocaulescent counterparts. As a result, chollas tend to place in the succulent tissue only at night, is a requisite for occur in the hotter and drier parts of the desert and prickly crassulacean acid metabolism, and has been shown to increase pears in the cooler places, particularly sites with winter rain. with decreasing temperature. The intensified heat build -up in stems is beneficial in cool Other adaptations are apparent in the platycaulescent (usually higher elevation) parts of the desert but can be shrubby stem succulent life form. In searching for a reason harmful in mid -summer at the lower (and hotter) elevations. why prickly pears seem to be more healthy and abundant on Heat load in a prickly pear pad can be reduced to near that in a rolling hills and moderate slopes in the Sonoran Desert than in cholla joint by favorable orientation parallel to the rays of the flat situations, we discovered that they possess a unique sun. Although pads of most prickly pear species can not track method for improving their own habitat under such condi- the sun because of their relative inflexibility, it can be shown tions! An examination of clumps of prickly pears growing on that the majority of pads on a plant are often oriented in hillsides showed that they were in pockets of exceptionally relation to the sun's rays at the most critical time of day. good soil which was most pronounced on the uphill side. As At lower elevations more pads tend to run in a northeast to the prickly pear grows, the flat stem segments form a southwest direction and will be parallel to the sun's rays from decumbent chain parallel to the contour line of the slope. Each early to mid afternoon. At higher elevations more pads tend to segment roots into the soil and a virtual dam is produced run in an east -to -west or southeast -to- northwest direction, which impedes the downhill erosion of soil. As good soil being perpendicular to the rays of the sun from mid -morning builds up around the plant, stem segments become buried in Representative platycaulescent stem succulent: Beavertail Cactus (Opuntia basilaris), showing pads oriented to take full advantage of winter and spring sun. Photo by Leslie Ely.

Representative cylindrocaulescent shrubby stem succulent: Teddy -Bear Cholla or "lumping Cactus" (Opuntia bigelovii) in the Sacramento Mountains near Needles, California. Photo by Mark Dimmitt. Along a trail at the Boyce Thompson Southwestern Arboretum a Curve -Billed Thrasher has built a nest in the protection of a sharp -spined cylindrocaulescent shrubby stem succulent, Chain -Fruit Cholla (Opuntia fulgida). Many visitors to the Arboretum at Superior have fond memories of having walked under this arching platycaulescent shrubby stem succulent on a side path in the cactus garden. Representative winter -deciduous Representative leafless green- stemmed microphyllous perennial: Mesquite (Prosopis perennial: Crucifixion Thorn (Holacantha emoryi) at velutina) at the Boyce Thompson Southwestern the Boyce Thompson Southwestern Arboretum. Photo by Arboretum. Photo by Carol D. Crosswhite. Carol D. Crosswhite.

Representative green- stemmed microphyllous perennial: Foothill Palo Verde (Cercidium microphyllum) at the Boyce Thompson Southwestern Arboretum. Photo by lames Weidlein. Desert Mistletoe (Phoradendron californicum) growing on branch of Catclaw Acacia at the Arboretum combines several life form characteristics. Although it is a leafless green- stemmed perennial, it is also a parasite.

whole or in part but new adventitious roots arise at higher Leafless Green -Stemmed Perennials levels and grow into the deepening pocket of soil. Water The survival strategy of this life form is to do away with loss running off the hillside soaks into the soil pocket and as the of water by leaves simply by eliminating the leaves. This pocket deepens over the years through soil accumulation, the requires transfer of all photosynthetic processes to stem water supply to the plant improves. But since each pocket is a tissues. The success of this syndrome in the Sonoran Desert rather discrete entity, and because of the natural drainage of goes against the classic rationale in textbooks for localization the hillside, together with capture and storage of the water by of plant functions to specialized organs -the root, stem and the prickly pear, rather complete soil desiccation is apt to leaf. The typical leaf, so successful in displaying chlorophyll in occur between rains. This ensures that most other life forms sunlight in most temperate and tropical situations, unfor- will be incapable of occupying the soil pocket permanently tunately is in such intimate contact with the air that heat and and will give little if any competition to this very successful wind in the desert can be extremely desiccating. This survival succulent life form. strategy gives up proliferation of photosynthetic surface in The Javelina ( Pecari tajacu), a pig -like creature, is a natural favor of a defensive posture of conservatism and consolidation. enemy of the prickly pear, eating the pads even despite the In this life form and related ones the strategy is one of the most spines. In this regard it is interesting to note that several effective in the entire Sonoran Desert. species of prickly pears common in Javelina habitat are Cacti also are leafless green- stemmed plants but are further actually arborescent (tree-like), apparently sacrificing decum- separated in the present classification into various types of bency and habitat improvement through soil -pocket formation stem succulents. An intermediate condition between the in favor of protection from being eaten! present life form and a typical plant with root, stem and leaf is 154 Desert Plants 5 (4) Winter 1984

In this particular plot the Boyce Thompson Southwestern Arboretum experimented with various species of chamaephytes, therophytes, tuberous geophytes and low semi -woody bushes.

The Arboretum at Superior was a pioneer in the study of physiological ecology of various life forms capable of being grown in the desert. Photographed here is an experiment involving evergreen hardwood perennials. Crosswhite and Crosswhite Desert Life Forms 155

Representative low leafy semi -woody bush: Goose f oot Bursage (Ambrosia chenopodi f olia) at Arroyo Seco, Baja California del Norte. Photo by Kent Newland.

seen in certain green- stemmed microphyllous perennials which in the Raunkiaer system. The survival strategy of this life form are drought- deciduous like Palo Verde (Cercidium) or Smoke in the desert has been difficult to appreciate and a clear -cut Tree (Dalea spinosa). comprehension has been missing in the literature. By means of genetically fixed leaf reduction and loss Evidence is accumulating that flexibility is the key to coupled with proliferation of chlorophyll in stem tissues, success, however. Studies of a representative species, Brittle - many phylogenetic lines have separately given rise to species bush (Encelia farinosa), have shown that there is a marked having the present life form. There is a distinct tendency for seasonal variation in leaf size, shape and number correlated stems in this life form to be thorny to ward off animals which with soil moisture availability. Cunningham and Strain (1969) might eat them. "Crucifixion Thorn" examples in the Sonoran and Walter (1931) have presented data to indicate that Desert include trees in the Celastraceae family (Canotia Brittlebush adjusts rather precisely to the changing seasons of holacantha) and Koeberliniaceae family (Koeberlinia spinosa), the desert through such leaf changes which in turn alter as well as a shrub in the Simaroubaceae family (Holacantha diffusion of water vapor and resistance to carbon dioxide. emoryi). Less thorny examples are Mormon Tea or Cañutillo These alterations change the water status of the plant and the (Ephedra, related to conifers) and Desert Mistletoe (Phoraden- capacity for carbon dioxide exchange. Shreve (1951) inferred dron Cali f ornicum). The latter species is also treated under the that seasonal reduction of leaves and stems, as well as the parasite category in the life form classification. indeterminate nature of growth and branching, were of value in characterizing this life form. Apparently these are the Low Leafy Semi -Woody Bushes outward manifestations of the seasonal physiological changes According to Shreve (1951) this is the most successful life discussed above. form of the Sonoran Desert insofar as its individuals "vastly In the Sonoran Desert the low leafy semi -woody bush outnumber any other life form in the entire region." The plants category includes plants like Bursage (Ambrosia subgenus were referred to by Shreve as "semi- shrubs." They would Franseria), Saltbush (Atriplex), Jimmyweed (Aplopappus), and represent a segregant within the "nanophanerophyte" category Brittlebush ( Encelia). This sclerophyllous evergreen hardwood bush, Jojoba (Simmondsias chinensis), was grown in a lysimeter at the Boyce Thompson Southwestern Arboretum in order to monitor seasonality of water use and root development.

Evergreen Hardwood Bushes Jojoba is an excellent example of a shrub with sclerophylls- This life form has deep roots which extend to water reserves thick and leathery leaves. In contrast to the leafless green- far below the landscape surface. Although such soil strata stemmed perennial which has eliminated harsh interaction of experience less fluctuation in moisture than those near the leaves with the environment by eliminating the leaves, the surface, there are nevertheless locations where this life form sclerophyllous shrub eliminates the harsh interaction by becomes severely drought stressed. The adaptations to cope insulating the leaves rather than losing them. The thick and with this stress are manifested primarily in the leaves. leathery appearance of sclerophylls is due to the presence of a By the leaves being evergreen the plants avoid using the thick, coarse, often multiseriate epidermis. A thick waxy energy which would have been needed to periodically produce cuticle is also present and the stomata are sunken. Al -Ani et al. new crops of leaf biomass. Also, such evergreen leaves stand ( 1972) demonstrated that Jojoba could photosynthesize atvery ready to photosynthesize whenever favorable conditions are high temperatures (40 ° -47 °C) and under conditions of ex- present, even if somewhat fleetingly. The two major xero- tremely low leaf water potentials. During periods of drought morphic leaf adaptations in this life form can be exemplified the experimental plants were able to maintain a favorable by the sclerophylls of Jojoba ( Simmondsia chinensis) and the carbohydrate budget by reducing carbon loss and actually microphylls of Creosotebush (Larrea tridentata). achieving carbon gain. Representative sclerophyllous evergreen hardwood bush: Guayacán (Viscainoa geniculata) at Catavina, Baja California del Norte. Photo by Kent Newland.

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Representative microphyllous evergreen hardwood bush: Creosotebush (Larrea tridentata) near Fort McDowell Indian Reservation, Maricopa County, Arizona. Photo by Frank S. Crosswhite. 158 Desert Plants 5 (4) Winter 1984

Representative drought- deciduous flagelliform perennial: Ocotillo (Fouquieria splendens) at the Boyce Thompson Arboretum. Photo by Carol D. Crosswhite.

Creosotebush is a good example of a shrub with micro - Drought -Deciduous Flagelliform Perennials phylls -tiny leaves adapted to arid conditions. The micro - This is the (perhaps unique) life form of the Ocotillo ( Fou- phyllous shrub reduces water loss from the leaves by altering quieria, defined to exclude Idria). Its survival strategy is to grow the aerodynamics of air -flow around them. Through separating on thin soils avoided by most other life forms, relying on a the total leaf surface into many tiny segments, the aero- sophisticated mechanism of precisely regulated physiological dynamic force (which also causes airplanes to rise!), created by responses to allow recurrent periods of high metabolic rate and air moving over the leaves, is reduced, resulting in very photosynthetic activity alternating with periods of dormancy. minimal lifting of moisture from the stomata. In the case of According to Shreve (1951) Ocotillo may produce and lose as Creosotebush, the leaf epidermis is also covered with a many as six or seven sets of leaves during a single year. varnish -like layer that further reduces water loss. Hull et al. The life form produces a rosette of flagelliform wand -like (1971) studied physiological adaptations in the species. A low stems from a thickened indurate caudex -like base. Scattered rate of photosynthesis (indicating dormancy) is apparently uniformly along the wands are stubby, fat little sunken triggered by low tissue water potential rather than high branches hidden in the axils of spines which derive from the temperature. Dechel et al. (1972) found a high stomatal hardened persistent petioles of the primary leaves. These tiny resistance to water loss. branchlets produce new leaves extremely rapidly when soil is Examples of this life form with sclerophylls, aside from moist. When the plants are in leaf, metabolism and photosyn- Jojoba, are Sonoran Caper (Atamisquea emarginata), Jito (For - thesis proceed rapidly. When the leaves fall, the life form chammeria watsoni), Yerba de la Flecha (Sapium biloculare), becomes extremely dormant, with all physiological processes and Jacquinia pungens. The plant known as Guayacán ( Vis- slowed to an extreme. Cells of the inner bark which are filled cainoa geniculata) in Baja California has sclerophylls for older with resin seem to be related to drought resistance during leaves and loses its more mesic younger leaves during times of dormancy. The hard, indurate caudex -like structure at the base severe drought stress. Examples of evergreen hardwood bushes of the plant seems to be involved with resin dynamics, with with microphylls, aside from Creosotebush, are Crucillo equalizing the osmotic balance among stems, and with medi- (Condalia warnockii) and Desert Hackberry (Celtis pallida). ating the precise timing of leaf- production and leaf -shed. Crosswhite and Crosswhite Desert Life Forms 159

Desert life forms are readily adaptable to landscape architecture. In this designed landscape a drought- deciduous f lagelli f orm perennial is tucked neatly away behind a platycaulescent shrubby stem succulent. 160 Desert Plants 5 (4) Winter 1984

Representative drought- deciduous sarcocaulescent perennial: Elephant Tree (Bursera sp.) on Angel del la Guarda Island, Baja California del Norte. Photo courtesy of Arizona- Sonora Desert Museum. Al Morgan, photographer.

Drought -Deciduous Sarcocaulescent Perennials Drought -Deciduous Large -Leaved Perennials This life form is characterized by a stout, swollen trunk According to Shreve (1951), the Sonoran Desert examples of which is out of all proportion to other parts of the plant. Shreve this group are all winter -deciduous species which have added (1951) credited such plants as being second only to the stem the additional xerophytic response of not leafing out in spring succulents "in giving the vegetation of the Sonoran Desert its or summer until adequate rainfall occurs. This represents a characteristic physiognomy." Although the swollen trunks degree of improvement over the survival strategy of the typical lack some of the characteristics of the typical succulent, they winter -deciduous perennial, since there is a mechanism to do contain a large amount of very moist tissue in a relatively ensure that energy and water will not be used to produce what discrete body mass. Several distinct phylogenetic lines have might prove to be an aborted growth cycle. The cycle simply converged toward this life form. It is noteworthy that sarco- will not begin unless adequate moisture is present. There is an caulescent perennials generally represent the closest approach analogy here with the ephemeral therophytes which have to succulentism in their particular families. germination inhibitors in their seed coats (which make certain Although the survival strategy seems to be intermediate that germination will occur only after heavy rains). Just as the between that of the drought- deciduous tree and that of the typical ephemeral survives long hot and dry periods in the typical stem succulent, it appears to be more than a mere seed, so too must the drought- deciduous large -leaved perennial intermediate condition. When the plants are leafed out, they be capable of lying dormant through such stressful periods. can function more or less like a typical tree. Through The analogy can be taken a step further by noting that whereas abscission of the more mesic structures (leaves), the plants can the ephemeral seems to be a specialized desert adaptation of periodically die back to the extremely xerophytic swollen part. the temperate annual, the present life form is a specialized With this technique, the life form can grow in habitat that desert adaptation of the temperate woody perennial. would be seasonally unfavorable for the typical tree. One disadvantage of this life form is that if good summer Drought- deciduous sarcocaulescent perennials of the So- rain does occur, the plants will not yet be leafed out and will noran Desert include Copalquín (Pachycormis discolor), Boo - not be ready to photosynthesize as quickly as the normal jum Tree or Cirio (Idria columnaris), and species of Elephant winter -deciduous perennial (which typically would have leafed Tree (Bursera). continued on page 186 Crosswhite and Crosswhite Desert Life Forms 161

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One section of the cactus garden at the Boyce Thompson Southwestern Arboretum is dominated by Boojum Trees (Idria columnaris). The pair in this 30-year-old photograph have prospered to the point where they are now thought to be the largest sarcocaulescent perennials north of Mexico. 162 Desert Plants 5 (4) Winter 1984

Introduction The Acanthaceae of The Acanthaceae are a predominantly tropical family comprising some 250 genera with about 3000 species. Al- though 18 species are indigenous to the southeastern United the Southwestern States (Long, 1970), the family is best represented in this country in the arid Southwest where 25 species in 11 genera United States are presently known to be native. The family is not considered to be of major economic importance, however, numerous alien species are commonly cultivated in the Southwest for their attractive flowers (e.g. species of Acanthus, Justicia, and Thomas F. Daniel Ruellia). In addition, most of the southwestern species provide excellent browse. Dept. of Botany and Microbiology Arizona State University In this study, the 25 naturally occurring species in the southwestern United States are treated. The Southwest is defined as comprising southern California (south of 35° N latitude), Arizona, New Mexico, and the trans -Pecos region of western Texas. This region includes those portions of the Sonoran and Chihuahuan Deserts occurring in the United States. Indeed it is these arid deserts in which the majority of species of southwestern Acanthaceae are found. Although treatments of the Acanthaceae are provided in each of the state floras covering this region (Munz, 1959; Kearney and Peebles, 1960; Martin and Hutchins, 1981; Correll and Johnston 1970), numerous name changes, several changes in taxonomic status, and range extensions for most taxa make an updated and regional treatment desirable. In addition, six species not treated in the state floras are now known to occur in this region and are considered here. Although Gray (1880) listed four species of Acanthaceae as potentially occurring in California, only one ( Justicia cali- fornica) has been documented from that state. The species occurs in passes and on the eastern slopes of the peninsular ranges, eastward through the Sonoran Desert (cf. Colorado Desert) to the Colorado River. Two other species of the family, Carlowrightia arizonica and Anisacanthus thurberi, will likely be found along the southeastern border of the state. Twelve species were recognized by Kearney and Peebles (1960) as occurring in Arizona. One of those, Dicliptera pseudoverticillaris Gray, is no longer maintained as a distinct species and two additional species have been discovered in the state, for a total of 13 species. Within Arizona, species of Acanthaceae are restricted in distribution to the southern and central part of the state. The rapid rise in elevation in central Arizona and the resulting changes in vegetation type and winter temperatures apparently form a natural boundary to the northward migration of the family. The recent flora of New Mexico (Martin and Hutchins, 1981) lists 10 species of Acanthaceae as occurring in that state. Abstract Three species cited in that work (Ruellia metzae, Carlowrightia The predominantly tropical family Acanthaceae are repre- torreyana, and Dyschoriste linearis) are not presently known sented in the southwestern United States by 25 species in 11 from New Mexico and four others are (Siphonoglossa pilosella, genera. Within this region, species of Acanthaceae are found C. texana, Tetramerium nervosum, and Justicia wrightii.) Thus primarily in the Sonoran and Chihuahuan Desert regions. in this treatment, 11 species are recognized as occurring in the Name changes, changes in taxonomic status, and range state. Within New Mexico, species of Acanthaceae are re- extensions update the treatments of Acanthaceae in state stricted to the southern part of the state. Their range is floras which cover the region. In addition, six species not bounded by high mountains to the northwest and grassland previously included in state floristic manuals are documented communities to the east. The Acanthaceae flora of New from the Southwest. Keys to and descriptions of each genus Mexico is enriched by incursions of species from both the and species are provided. Information on synonymy, distri- Sonoran and Chihuahuan Desert regions. Other species which bution, habitat preference, and phenology of each species is should be sought in the state include: Carlowrightia arizonica, also given. C. serpyllifolia, and Ruellia nudiflora. Daniel Acanthaceae 163

Wasshausen (1966) reported 14 species of Acanthaceae from 1. Fertile stamens 2. the trans -Pecos region of Texas. With several additions to the 4. Leaves alternate or clustered; inflorescences borne on Acanthaceae flora of western Texas, 18 species are now known long, scaly peduncles, the scales coriaceous and imbri- to occur there. The Chihuahuan Desert is considerably richer cate; bracts 3- toothed at apex; retinacula papilliform; in taxa of Acanthaceae than is the Sonoran Desert and this fact seeds minute, 0.5 - 0.7 mm long Elytraria is emphasized by the comparatively large number of species in 4. Leaves opposite (rarely subopposite in some individuals); this region of Texas which encompasses only nine counties. inflorescences not borne on scaly peduncles; bracts (if No species of Acanthaceae are endemic to the region present) not 3- toothed; retinacula well- developed, hook- covered by this treatment, however 17 of the 25 species are like; seeds large, 1.5 - 7 mm long. either endemic or largely restricted to one of the major desert 5. Stems hexagonal- ridged; flowers and bractlets sub- regions of the southwestern United States and northern tended by 2 conspicuous cordate to deltate to Mexico. Thirteen species (Anisacanthus linearis, A. puberulus, reniform, sometimes basally fused bracts; lower lip of Stenandrium barbatum, Siphonoglossa pilosella, Carlowrigh- corolla entire; placenta separating from mature cap- tia parvifolia, C. linearifolia, C. serpyllifolia, C. mexicana, C. sule valves Dicliptera texana, C. torreyana, Justicia warnockii, J. wrightii, and Ruellia 5. Stems terete to quadrate (often striate); flowers and parryi) can be considered as either entirely or largely Chi - bractlets not subtended by bracts as described above; huahuan in distribution. In the Southwest, these species occur lower lip of corolla shallowly to deeply trilobed; pla- primarily in trans -Pecos Texas and southeastern New Mexico. centa remaining attached to mature capsule valves. Four species are primarily Sonoran in distribution (Anisacan- 6. Stamens more or less appressed to upper lip of thus thurberi, Justicia calf f ornica, J. sonorae, and Siphonoglossa corolla, the anthers opening toward the lower lip; longiflora). They occur in southern California, Arizona, and thecae usually conspicuously unequally inserted southwestern New Mexico (although S. longiflora has been on filament, at least the lower one apiculate or reported from one locality in trans -Pecos Texas). The eight prominently spurred. remaining species (Carlowrightia arizonica, Dicliptera resu- 7. Corolla tube slender and cylindric, ampliate pinata, Dyschoriste decumbens, Elytraria imbricata, Henrya only at apex if at all Siphonoglossa insularis, Justicia candicans, Ruellia nudiflora, and Tetra - 7. Corolla tube not cylindric, ampliate from below merium nervosum) have considerable ranges outside of these the middle Justicia desert regions. They are widely distributed species and most of 6. Stamens more or less appressed to lower lip of them show a great deal of morphological variation throughout corolla, the anthers opening toward the upper lip; their ranges. thecae equally or subequally inserted on filament, The region of southeastern Arizona and southwestern New rounded to acute at base, lacking any basal Mexico (Fig. 1 a), which lies between the two major deserts and appendages. just north of the Sierra Madre Occidental in Mexico, contains 8. Corolla somewhat fleshy, concolorous, red, isolated pockets of Chihuahuan Desert vegetation and large orange, or pinkish, 30 - 57 mm long, the lobes of tracts of desert grassland. This region apparently serves as the lower lip similar in form both a filter and a barrier with respect to the migration of Anisacanthus Acanthaceae. Some Chihuahuan Desert species (e.g. Carlo - 8. Corolla not fleshy, white, blue or purplish with wrightia linearifolia) reach their westernmost outposts here yellow and /or maroon markings on the upper and certain Sonoran Desert species (e.g. Siphonoglossa longi- lip, 5.5 - 18 mm long, the central lobe of the flora) have undoubtedly traversed this region in their migration lower lip dissimilar in form from the lateral into the Chihuahuan Desert. lobes (except in Carlowrightia linearifolia and In this treatment, a key to the eleven genera of southwestern C. parvifolia in which the three lobes are nearly Acanthaceae is followed by a short diagnosis of each genus, a identical). key to the species, and a description of each species. Pertinent synonymy, habitat information, and flowering times are also 9. Inflorescence of densely bracteate, 4 -sided provided for each species. Nomenclatural, taxonomic, and spikes; bracts 3.5 - 5 mm wide, the surfaces distributional notes are provided where this treatment differs prominently veined, the margin hirsute - from other accounts. Maps showing the distribution by ciliate, the apex falcate -mucronate; calyx county of each species are also included. 4 -lobed Tetramerium 9. Inflorescence of lax to dense spikes or Key to Genera of Southwestern Acanthaceae racemes (not 4- sided) or the flowers axillary; 1.Fertile stamens 4. bracts (if present) 0.3 - 2 (- 4) mm wide, the 2. Anthers monothecous; plants dwarf perennial herbs to surfaces, margin, and apex not as above; 10 cm tall with leaves clustered at or near ground level calyx 5- lobed. Stenandrium 10. Bractlets oblanceolate, fused along one 2. Anthers bithecous; perennial herbs or subshrubs to 5 dm side from the base to the apex; capsule 5 - tall with leafy stems. 7 mm long; seeds pubescent 3. Corolla 15 - 25 mm long; thecae with pointed basal Henrya spurs; seeds 4 or fewer per capsule 10. Bractlets subulate to linear to lanceolate Dyschoriste to ovate to triangular, not fused; capsule 3. Corolla 25 - 50 mm long; thecae lacking basal spurs; 7-12.5 mm long; seeds lacking tri- seeds 6 or more per capsule Ruellia chomes Carlowrightia 164 Desert Plants 5 (4) Winter 1984

Anisacanthus Nees wide, pubescent like bracts. Calyx 5 - 8 ( -10) mm long, the lobes Shrubs; calyx 5- lobed; corolla usually reddish or orange, lance -subulate, glandular. Corolla pinkish, 37 -57 mm long, relatively large, with an ampliate tube and a bilabiate limb upper lip 18 - 25 mm long, lower lip 20 - 27 mm long. Stamens comprising an entire to emarginate upper lip and a 3 -lobed 22 - 30 mm long, the thecae 2.5 - 3.8 mm long. Capsule stipitate, lower lip; stamens 2, anthers bithecous, the thecae equally to 20 - 22 mm long, glabrous. Seeds 5.5 - 6 mm long. (March - June subequally inserted, lacking basal appendages; seeds 4 or fewer and October). per capsule. A species with very much the aspect of A. thurberi, but Approximately 20 species, centered in Mexico but reported differing in habit, corolla length and color, and capsule length. from South America. Restricted in distribution to the Chihuahuan Desert region of 1. Leaves sessile, linear to lance -linear, 1- 3 (- 6) mm wide, the trans -Pecos Texas and north -central Mexico where it occurs surfaces glabrous. 1. A. linearis along arroyos (or on alluvial fans or flats) in desert scrub at 1. Leaves subsessile to petiolate, lanceolate to ovate to oblan- elevations of 925 to 2100 meters (Fig. lb). ceolate, 2 - 35 mm wide, the surfaces pubescent. Representative specimens examined: Texas: Brewster Co.: 2. Corolla pinkish, 37 - 57 mm long; capsule 20 - 22 mm near Marathon, Texas Hwy. Dept. T377 (ARIZ, SRSC, TEX); long; plants of Texas. 2. A. puberulus Presidio Co.: 5 mi SSW of Shafter, Muller 5004 (ARIZ). 2. Corolla orange -red, 30 - 40 mm long; capsule 12 - 16 mm long; plants of Arizona and New Mexico. 3. A. thurberi 3. Anisacanthus thurberi (Torr.) Gray, Syn. Fl. N. Amer. 2(1): 328. 1 878. Drejera thurberi Torr. in Emory, Rep. U.S. & Mex. Bound. 1. Anisacanthus linearis (Hagen) Henrickson & Lott, Surv. 2(1): 124. 1851. Brittonia 34: 175. 1982. Shrub to 1.5 m tall. Younger stems subquadrate, the inter - A. insignis Gray var. linearis Hagen, Ann. Missouri Bot. nodes pubescent with flexuose to appressed eglandular tri- Gard. 28: 396. 1941. chomes to 0.8 mm long, these mostly concentrated in 2 lines, Erect shrub to 2 m tall. Younger stems terete, glabrous or the flower bearing apex of the younger stems pubescent with sparsely pubescent in 2 lines with retrorse trichomes to 0.2 mm an understory of eglandular and glandular, straight to flexuose long. Leaves sessile, linear to lance -linear, 10 - 50 mm long, 1- 3 trichomes to 0.2 mm long and usually with an overstory of (- 6( mm wide, cuneate at base, acute at apex, the surfaces glab- scattered to dense eglandular, straight to flexuose trichomes rous. Flowers in axils of reduced upper leaves or bracts along to 1 mm long (hirsute), the nodes pubescent with the latter upper portions of stems. Bracts linear to lanceolate to ovate, type trichomes. Leaves usually forming dense clusters along 1.5 - 8 mm long, 0.8 - 1.5 (- 2.5) mm wide, glabrous to sparsely the older stems, subsessile to petiolate, the petioles to 3 (- 14) pubescent with trichomes 0.05 mm long, often glandular. mm long, the blades lanceolate to ovate to narrowly elliptic to Bractlets linear -subulate, 1.5 - 3 mm long, 0.5 - 1 mm wide, pu- oblanceolate, 7 -22 (- 65) mm long, 2 - 8 ( -35) mm wide, acute to bescent like bracts. Calyx 4 - 7 mm long, the lobes subulate, attenuate at base, acuminate to acute at apex, the surfaces glandular. Corolla red or orange -red, 38 - 50 mm long, upper lip hirsute. Flowers usually borne in the axillary leaf clusters or 18 - 25 mm long, lower lip 22 - 30 mm long. Stamens 28 - 32 mm rarely in leaf axils along the younger stems. Bractlets subulate long, the thecae 3.8 - 4 mm long. Capsule stipitate, 16 - 22 mm to linear -lanceolate or becoming foliose, 2 - 15 (- 20) mm long, long, glabrous. Seeds 5 - 6 mm long. (June - September). 0.5 -1.5 (- 6) mm wide, pubescent with trichomes 0.05 - 0.5 mm A species restricted in distribution to the Chihuahuan long, often glandular. Calyx (at anthesis) 6.5 - 13 mm long (12 - Desert region of trans -Pecos Texas and north -central Mexico 16 mm long in fruit), the lobes subulate, the outer surface where it occurs along arroyos in desert scrub at elevations pubescent like the younger stems although the glands more from 1000 to 1600 meters (Fig. lb). numerous. Corolla orange -red, 30 - 40 mm long, upper lip 10 - Representative specimen examined: Texas: Brewster Co.: 20 mm long, lower lip 11 - 20 mm long. Stamens 20 - 35 mm Chisos Mts., Painted Gap, Warnock 905 (ARIZ, SRSC, TEX). long, the thecae 3 - 3.5 mm long. Capsule 12 - 16 mm long, glabrous. Seeds 5 - 7 mm long. (February - November). Restricted in distribution to the southwestern United States 2. Anisacanthus puberulus (Torr.) Henrickson & Lott, and adjacent regions of northwestern Mexico where it occurs Brittonia 34: 172. 1982. on rocky slopes and especially along arroyos and streams in Drejera puberula Torr. in Emory, Rep. U.S. & Mex. Bound. Sonoran Desert scrub and desert grassland at elevations from Surv. 2(1): 123. 1859. 550 to 2200 meters (Figs. lb, 2a). A. insignis Gray, Syn. Fl. N. Amer. 2(1): 457. 1886. Representative specimens examined: Arizona: Apache Co.: Erect shrub to 3 m tall. Younger stems subquadrate, evenly White Mts., Schroeder s.n. (ARIZ); Cochise Co.: 1.4 mi NW of pubescent with flexuose trichomes 0.2 - 0.7 mm long, becoming Portal, Daniel 174 (ASU); Graham Co.: Goat Mtn., McGill 2372 pubescent in 2 lines with age. Mature leaves petiolate, the (ASU); Gila Co.: Three Bar Game Mgt. Area, Tonto Natl. Forest, petioles to 17 mm long, the blades lance -ovate to ovate, 21- 87 Pase s.n. (ASU); Greenlee Co.: Dix Creek, Niles and Bostick 985 mm long, 5 - 30 mm wide, rounded to acute at base, acute to (ARIZ); Maricopa Co.: 0.8 mi. SW of Canyon Lake Lookout, Keil acuminate -falcate at apex, the surfaces pubescent. Flowers 1149 (ASU); Mohave Co.: 40 mi. S of Kingman, Denton 1435 usually appearing before the leaves in axillary clusters or short (ASU); Pima Co.: 5 mi. W of Arivaca, Lehto and Broome 22707 spicate racemes at the nodes of the previous season along the (ASU); Pinal Co.: ca. 2 mi. S of Roger's Trough, McGill 1307 upper portion of the stems. Bracts of axillary racemes elliptic, (ASU); Santa Cruz Co.: 4 mi. W of Patagonia, Carufel 15 (ASU); 2 - 5 mm long, 1 mm wide, densely glandular. Bractlets lance - Yavapai Co.: 6 mi. NE Seven Springs, Lehto and Reeves 20145 subulate to linear to oblanceolate, 2 - 4 mm long, 0.5 - 1.5 mm (ASU); Yuma Co.: Kofa Mts., Tunnel Springs Canyon, Lehto and Daniel Acanthaceae 165

Reeves 20075 (ASU). New Mexico: Grant Co.: Mangas Springs, Flowers solitary or several, pedunculate from leaf axils, 18 mi. NW of Silver City, Metcafe 113 (ARIZ, NMC); Hidalgo especially along the upper portion of the stem. Bractlets linear, Co.: Guadalupe Canyon, 15 mi. E of jet. rd. to Douglas, Hess 1- 8 mm long, 0.2 - 0.8 mm wide. Calyx 3 - 5 mm long, the lobes 1817 (ARIZ, NMC); Luna Co.: 13 mi. S of Deming, Hess and subulate. Corolla light purple with dark purple lines in a Tyznik 3244 (ARIZ, NMC). whitish eye on the upper lip, 6.5 - 9 mm long, the upper lip 4.5 - 7 mm long, the lower lip 4.5 - 7 mm long. Stamens 4 - 6 mm long, the thecae yellowish, 0.8 - 1 mm long. Capsules 7 - 9 mm Carlowrightia Gray long, glabrous or sparsely pubescent at apex. Seeds usually 2 Suffrutescent herbs or shrubs; calyx 5- lobed; corolla white, per capsule, concavoconvex, 3 - 3.9 mm long, testa tuberculate blue, or pinkish, relatively small, with a slender, scarcely on concave side, margin dentate. (May - October). ampliate tube and a bilabiate limb comprising an emarginate Known only from the Chihuahuan Desert region of trans - upper lip and a 3 -lobed lower lip; stamens 2, anthers bithecous, Pecos Texas and Coahuila where it occurs in limestone the thecae equally to subequally inserted, lacking basal crevices and along rocky washes in desert scrub at elevations appendages; seeds 4 or fewer per capsule. from 1200 to 1500 meters (Fig. lc). Twenty species are recognized in this predominantly Mexi- Representative specimens examined: Texas: Brewster Co.: can genus. locality not specified, Warnock 44392 (TEX); Pecos Co.: Sierra 1. Corollas blue, subactinomorphic, the lower- central lobe Madera, 22 mi. S of Ft. Stockton, Warnock and McVaugh not conduplicate; anthers yellow; leaves 4 - 35 times longer 8706 (SRSC). than wide. 2. Young stems strigillose, the trichomes recurved, 0.2 -0.6 (- 1) mm long; corollas 6.5 - 9 mm long; capsules 7 - 9 mm 2. Carlowrightia linearifolia (Torr.) Gray, Proc. Amer. long; seed margin dentate 1. C. parvifolia Acad. Arts 13: 364. 1878. Not C. linearifolia Lindau /1897). 2. Young stems puberulent, the trichomes straight, less Schaueria linearifolia Torr. in Emory, Rep. U.S. & Mex. than 0.2 mm long; corollas 9 -11 mm long; capsules 10.5 - Bound. Surv. 2(1): 123. 1859. 12.2 mm long; seed margin entire 2. C. linearifolia Erect, openly branched shrub to 2 m tall. Younger stems 1. Corollas blue or white, bilabiate, the lower- central lobe terete, evenly pubescent with erect trichomes 0.02 - 0.10 mm conduplicate; anthers maroon; leaves 0.8 - 8 times longer long. Leaves often subopposite, sessile (rarely subsessile with than wide. petioles 0.5 mm long), the blades linear, 10 - 55 mm long, 0.5 - 2 3. Shoots glandular pubescent (glands inconspicuous in C. (- 3) mm wide, attenuate to acute at base, rounded to acute at arizonica); corolla 9 - 15 mm long. apex, surfaces pubescent. Flowers in bract axils in racemose or 4. Glandular trichomes conspicuous, 0.1- 0.7 mm long; thyrsoid axes, collectively forming a terminal, leafy panicle or eglandular trichomes disposed in 2, narrow, vertical thyrse. Bracts linear, (1.5 -) 3 - 20 (- 35) mm long, 0.4 -1 mm wide. lines along stems; leaves ovate to orbiculate; corollas Bractlets linear, 0.5 -10 mm long, 0.2 - 0.6 mm wide. Calyx 1.5 - blue 3. C. serpyllifolia 5.2 mm long, the lobes linear to triangular. Corolla lavender 4. Glandular trichomes inconspicuous, 0 1 mm long or blue with faint yellow eye streaked with purple on the upper less; eglandular trichomes evenly disposed along lip, (7.5 -) 9 -12 mm long, upper lip 4.5 - 8 mm long, lower lip 5 - 8 stems; leaves lanceolate to narrowly ovate; corollas mm long. Stamens 5.5 - 6 mm long, the thecae golden yellow, white 4. C. arizonica 1.1 -1.9 mm long. Capsules 10.5 -12.2 mm long, glabrous. Seeds 3. Shoots eglandular or with glandular inflorescence axes 4 per capsule, 3.8 - 4 5 mm long, testa papillose, margin entire. only in C. torreyana); corollas 6 - 10 mm long. (July - December). 5. Leaves elliptic -lanceolate to obovate, to 9 mm wide; Restricted in distribution to the Chihuahuan Desert region corollas blue 5. C. mexicana of the southwestern United States and adjacent regions of 5. Leaves ovate to orbiculate, to 30 mm wide; corollas north -central Mexico where it occurs in rocky washes and in white. the gravelly or sandy alluvium of arroyos in desert associations 6. Cauline trichomes recurved; inner bractlets ovate from 900 to 1750 meters (Fig. le). to lanceolate; corolla white with distinct maroon Representative specimens examined: Arizona: Cochise Co.: veins on each petal lobe; seed margin entire... ca. 2 mi. N of Portal, Barr 62 -841 (ARIZ); Graham Co.: near 6. C. texana Matthews, Shreve 4388 (ARIZ). New Mexico: Doña Ana Co.: 6. Cauline trichomes straight; inner bractlets subu- mesa W of Organ Mts., Wooten s.n. (NY, US); Grant Co.: ca. 3 late; corolla white with a yellow eye fringed with mi. N of Howell's Ridge, Little Hatchet Mts., Van Devender and maroon on upper lip; seed margin denticulate .. . Spaulding s.n. (ARIZ): Hidalgo Co.: Dog Mts., Mearns 2398 (DS, 7. C. torreyana NY, US); Luna Co.: Florida Mts., Barneby 2478 (NY); Sierra Co.: 20 mi. N of Rincon, Metcalfe 1281 (A, CAS, F, GH, MO, NMC, NY, UC, US); Socorro Co.: Socorro, Eggleston 16256 (F, MO). 1. Carlowrightia parvifolia Brandegee, Univ. Calif. Texas: Brewster Co.: Chisos Mts., Daniel 565 (CAS, DUKE, Pub. Bot. 4: 190. 1911. ENCB, F, GH, MICH, MO, NY, TEX, UC, US); Culberson Co.: E Spreading to erect, spindly subshrub to 5 dm tall. Younger slopes of Van Horn Mts., Warnock and Turner 8989 (LL, MICH, stems gray -canescent, quadrate to terete, evenly pubescent, SMU, SRSC, TEX); El Paso Co.: W edge of El Paso, Correll 22619 the trichomes eglandular, retrorse, (0.1 -) 0.2 - 0.6 ( -1) mm long. (LL, MO, NCU, SMU, UC, US); Hudspeth Co.: 10 mi. W of Sierra Leaves sessile, the blades linear to narrowly lanceolate, 3 - 24 Blanca, Warnock 13600 (LL, SRSC, TEX); Jeff Davis Co.: 5 mi. W mm long, 0.5 - 3 mm wide, acute at base, acuminate to acute at of Bloys encampment, Warnock 15970 (SRSC); Presidio Co.: ca. apex, upper surface glabrous, lower surface sparsely pubescent. 3.5 mi. NW of Presidio, Correll 33896 (LL, UC, US). 166 Desert Plants 5 (4) Winter 1984

SOUTHWESTERN UNITED STATES ANISACANTHUS

LINEARIS

PUBERULUS DESERT REGIONS THURBERI

CARLOWRIGHTIA DICLIPTERA

ARIZONICA

LINEARIFOLIA RESUPINATA + PARVIFOLIA TEXANA MEXICANA O SERPYLLIFOLIA 0 TORREYANA

DYSCHORISTE ELYTRARIA

DECUMBENS IMBRICATA

HENRYA JUSTICIA

CALIFORNICA

CANDICANS INSULARIS WARNOCKII SONORAE O WRIGHTII

Figure 1.Maps of the southwestern United States showing: bution of Dyschoriste; f, distribution of Elytraria; g, distribution a, Sonoran and Chihuahuan Desert regions and filter- barrier of Henrya; h, distribution of lusticia; i, distribution of Ruellia; j, region between them; b, distribution of Anisacanthus; c, distri- distribution of Siphonoglossa; k, distribution of Stenandrium; bution of Carlowrightia; d, distribution of Dicliptera; e, distri- 1, distribution of Tetramerium. Daniel Acanthaceae 167

RUELLIA SIPHONOGLOSSA

NUDIFLORA LONGIFLORA

PARRYI PILOSELLA

STENANDRIUM TETRAMERIUM

BARBATUM NERVOSUM

3. Carlowrightia serpyllifolia Gray, Proc. Amer. Acad. Representative specimens examined: Texas: Brewster Co.: Arts 21: 405. 1886. Oak Canyon, Correll and Correll 30621 (GH, LL, MO, SMU); El Decumbent to erect, globose and intricately branched or lax Paso Co.: W edge of El Paso, Correll 22602A (LL, MO, SMU, UC, and openly branched subshrub to shrub to 5 dm tall. Younger US); Presidio Co.: ca. 5 mi. W of Shafter, Hinckley 3220 (GH, stems quadrate to terete, pubescent with a mixture of eglandu- NY, US). lar and glandular trichomes, the eglandular trichomes sparse to dense, usually concentrated in 2 vertical lines, retrorse to 4. Carlowrightia arizonica Gray, Proc. Amer. Acad. erect, 0.05 - 0.90 mm long, the glandular trichomes usually Arts 21: 406. 1878. evenly disposed, (.05 -) 0.1 - 0.7 mm long. Leaves subsessile to Erect, much -branched subshrub to 1 m tall. Younger stems petiolate, the petioles 0.1 - 7(-14) mm long, the blades terete, evenly pubescent with erect to retrorse trichomes 0.05 (lanceolate) ovate to deltate to orbicular to elliptic to obovate, -0.50 mm long and with an inconspicuous understory of glands 2 - 24 mm long, 1.5 - 10 (- 16) mm wide, attenuate to acute to 0.1 mm long or less. Leaves sessile to petiolate, the petioles 0.2 rounded to truncate at base, acute to rounded at apex, surfaces - 8 mm long, the blades frequently conduplicate, lanceolate to sparsely to densely pubescent. Flowers usually borne in narrowly ovate to cordiform to elliptic, 3- 33 mm long, 1 - 9 glandular spicate axes. Bracts (lanceolate) ovate to orbicular- mm wide, cordate to truncate to acute at base, acute at apex, obovate (triangular), 0,5 - 2 (- 6) mm long, 0.5 -1.5 (- 4) mm wide. the surfaces pubescent. Flowers solitary or clustered in leaf Bractlets ovate to subulate, 0.6 - 2.1 (- 4) mm long, 0.4- 0 8 mm axils or in bract axils in spicate axes, Bracts narrowly wide. Calyx (1.5 -) 2 -4 (- 6 ) mm long, the lobes subulate. Corolla lanceolate to linear -subulate to triangular, 1- 7 mm long, 0.3 -1 (pink -purple) blue -purple with a yellow eye streaked with mm wide. Bractlets subulate to triangular, 0.8 - 8 mm long, 0.3 purple veins on the upper lip, 9 -15 mm long, the upper lip 7 -11 -1.3 mm wide. Calyx 1.5- 5 mm long, the lobes subulate. (- 14) mm long, the lower lip 7 - 14 mm long. Stamens 6.5- 8 Corolla white with a yellow eye streaked with maroon on the ( -10.5) mm long, the thecae maroon (turning black), 0.9-1.2 upper lip, 9 - 18 mm long, the upper lip 6 - 12 mm long, the mm long. Capsules 8.7 - 12 mm long, glabrous. Seeds 4 per lower lip 7 - 14 mm long. Stamens 5- 8 mm long, the thecae capsule, 3.5 - 5 mm long, testa papillose (rarely only minutely maroon, 1 - 1 3 mm long. Capsules 7.5 - 11 mm long, glabrous. so), margin dentate. (February - December). Seeds 4 per capsule, 3 - 4 mm long, testa papillose, margin Restricted in distribution to the Chihuahuan Desert region dentate. (November - May). of trans -Pecos Texas and north -central Mexico where it occurs Carlowrightia arizonica isa widely distributed (south- in washes, on rocky or gravelly hills, and along arroyos in desert western United States to northern Costa Rica) and taxonomi- scrub at elevations from 1000 to 1900 meters (Figs. lc, 2b). cally complex species with numerous diverse morphological 168 Desert Plants 5 (4) Winter 1984 forms. Two forms are recognizable in our region; one has short densely pubescent, the trichomes retrorse, 0.1- 0.5 (-1) mm (0.05 -0.20 mm) retrorse to retrorse- appressed eglandular long. Leaves petiolate, the petioles (1 -) 3 - 7 ( -20) mm long, the cauline trichomes, inflorescences of slender spicate axes with blades (deltate) broadly ovate to orbicular when larger, nar- bracts 1 -3 mm long, calyces 1.5 - 3.5 mm long, corollas 9 - 13 rowly ovate to elliptic when smaller, (2.5 -) 6 -16 (- 42) mm long, mm long, and capsules 7.5 -10 mm long; the other has generally (1.5 -) 3 - 11 (- 33) mm wide, truncate to rounded to acute (or longer (0.1-0.5 mm) erect to retrorse eglandular cauline oblique) at base, acuminate to acute (to rounded) at apex, trichomes, inflorescences of stout, leafy spicate axes with surfaces pubescent, especially along the veins. Flowers solitary bracts 3.5 - 7 mm long, calyces 2.5 - 5 mm long, corollas 10 - 18 or clustered in leaf axils, rarely borne in axils of bracts on mm long, and capsules 9 -11 mm long. The forms are fre- elongate, terminal, eglandular, spicate axes. Bractlets folia- quently encountered growing near one another. In our region, ceous, narrowly ovate to elliptic -lanceolate to linear, 2 -12 mm the species occurs on rocky slopes and in washes in both long, (0.5 -) 2.5 - 5 mm wide. Calyx (2.5 -) 3 - 6 mm long, the lobes Sonoran and Chihuahuan Desert scrub at elevations from 350 subulate. Corolla white with maroon veins on the lobes, 5.5 - 7 to 1300 meters (Fig. 1c). mm long, upper lip 3.5 - 5 mm long, lower lip 4 - 6 mm long. Representative specimens examined: Arizona: Cochise Co.: Stamens 3.3 - 5 mm long, the thecae maroon turning black, 0.5 - ca. 17 mi. E of Douglas, Daniel 1792 (ASU); Gila Co.: below 1 mm long. Capsules 7.5 - 12.5 mm long, glabrous. Seeds 4 per Whitlow Dam on Queen Creek, Getz and Engard 453 (DES); capsule, 4.2 - 6 mm long, testa (smooth) papillose, margin Graham Co.: Redfield Canyon, Haughey 546 (ASU); Maricopa entire. (March - November). Co.: South Mtn. S of Phoenix, Keil 178 (ASU); Mohave Co.: The species ranges from the Chihuahuan Desert region of Artillery Mts., Butterwick and Hillyard 4365A (ASU); Pima the southwestern United States and adjacent north -central Co.: Box Canyon in Santa Rita Mts., Daniel 173 (ARIZ, ASU, Mexico eastward into central and southern Texas. It occurs on GH, K, MICH, NCU, NY, UTEP); Pinal Co.: Aravaipa Canyon, limestone flats and hills or in the calcareous alluvium of ca. 10 mi. N of Mammoth, Daniel 170 (ARIZ, ASU, CAS, DUKE, arroyos in Chihuahuan Desert scrub, and in disturbed habitats F, GH, MICH, MO, NY, US); Santa Cruz Co.: near Patagonia, at elevations from 1000 to 1700 meters (Fig. lc). Harrison 7176 (ARIZ, NY, US); Yavapai Co.: S side of Harcuvar Representative specimens examined: New Mexico: Eddy Mts., Fischer 6666 (ASU); Yuma Co.: Kofa Mts., Lehto and Co.: Carlsbad, McKechnie 15 (MO, UNM); Texas: Brewster Co.: Reeves 20025(ASU, US). Texas: Brewster Co.: Sierra Quemada, Gilliland Canyon, Glass Mts., Warnock W324 (GH, MO, UC); Warnock and Wallmo 12304 (SRSC, TEX); Presidio Co.: ca. 25 Culberson Co.: near N end of Van Horn Mts., Waterfall 4560 mi. E of Presidio, Correll and Rollins 23682 (LL, NCU, UC). (GH); Jeff Davis Co.: Davis Mts., Earle and Tracy 153 (NY); Pecos Co.: 24 mi. NW of Sheffield, McVaugh 8204 (DS, F, GH, 5. Carlowrightia mexicana Henrickson & Daniel, Ma- MICH, SMU, US); Presidio Co.: ca. 2.5 mi. N of Shafter, drono 26: 32. 1979. Hinckley 1389 (F, LL, NY); Terrell Co.: ca. 18 mi. S of Sheffield, Prostrate to erect, suffrutescent perennial to 3.5 dm tall. Webster 330 (MICH, TEX). Younger stems quadrate to terete, pubescent with closely appressed or retrorse trichomes 0.1 - 0.2 (- 0.5) mm long, con- 7. Carlowrightia torreyana Wasshausen, Phytologia centrated in 2 lines or evenly disposed. Leaves subsessile to 12: 427. 1965. petiolate, the petioles 1- 3 (- 6) mm long, the blades elliptic - Schaueria parvifolia Torr. in Emory, Rep. U.S. & Mex. lanceolate to obovate, (4 -) 8 - 19 mm (- 29) mm long, 0.5 - 7 (- 9) Bound. Surv. 2(1): 122. 1859. mm wide, attenuate at base, acute to rounded at apex, surfaces Dianthera parvifolia (Torr.) Gray, Syn. Fl. N. Amer. 2: 330. sparsely pubescent. Flowers arising from leaf axils or from axils 1 878. of bracts in a helicoid or scorpoid spicate axis. Bracts (if present) Croftia parvifolia (Ton.) Small, Fl. Southeast. U.S. 1088, narrowly elliptic to linear, 2 - 7 mm long, 0.3 -1 mm wide. Bract - 1338. 1903. lets subulate to narrowly lanceolate, 0.8 - 3.5 mm long, 0.2 - 0.6 Decumbent to erect, suffrutescent perennial to 5 dm tall. mm wide. Calyx 3 - 5 mm long, the lobes subulate. Corolla light Younger stems often gray -canescent, quadrate to terete, evenly or dark blue with a yellow eye streaked with purple on the and densely pubescent, the trichomes erect to flexuose, (0.2 -) upper lip, 6.5 - 10 mm long, upper lip 3.5 - 6.5 mm long, lower lip 1 - 1.5 (- 1.9) mm long, often with an understory of erect to re- 4.5 - 6.5 mm long. Stamens 3.8 - 6 mm long, the thecae maroon trorse trichomes, 0.2 - 0.3 mm long as well. Leaves petiolate, the turning black, 0.5 - 0.8 mm long. Capsules 9 - 12 mm long, petioles 2 - 7 (- 15) mm long, the blades broadly ovate to orbi- glabrous. Seeds 4 per capsule, 3.5 - 5 mm long, testa smooth or cular when larger, ovate -elliptic when smaller, (5 -j 10 - 20 ( -40) papillose, margin entire to crenulate. (May -October). mm long, (3 -) 7 -13 (- 27) mm wide, truncate to rounded to acute Restricted in distribution to central and eastern portions of (or oblique) at base, rounded to acute at apex, surfaces the Chihuahuan Desert in trans -Pecos Texas and Coahuila pubescent. Flowers solitary or clustered in leaf axils, or more where it occurs on dry, rocky flats and in consolidated arroyo commonly in the axils of bracts in glandular spicate axes. gravel in desert scrub and oak chaparral at elevations of 1050 Bracts subulate to narrowly ovate, 1.5 - 4.9 mm long, 0.5 - 1.6 to 1410 meters (Fig. lc). mm wide. Bractlets subulate, 1.2 - 3 mm long, 0.3 - 0.7 mm wide Representative specimens examined: Texas: Brewster Co.: (bractlets subtending flowers in the leaf axils often larger). 17 mi. E of Marathon, Correll 34082 (GH, LL US); Pecos Co.: 25 Calyx 2.5 - 4 (- 5.8) mm long, the lobes subulate. Corolla white mi. SW of Ft. Stockton, Warnock 20002 (SRSC); Presidio Co.: with a yellow eye streaked with maroon on the upper lip, 7 - 9 North Chinati Mts., Warnock 19218 (SRSC). mm long, upper lip 4 - 5.5 mm long, lower lip 4.5 - 6 mm long. Stamens 4 - 5.5 mm long, anthers maroon turning black, thecae 6. Carlowrightia texana Henrickson and Daniel, Ma- 0.6 - 0.8 mm long. Capsules 8 - 12 mm long, glabrous. Seeds 4 per drono 26: 27. 1979. capsule, 4 - 4.8 mm long, testa papillose, margin crenulate to Erect to decumbent, suffrutescent perennial to 3.5 dm tall. dentate. (February - November) Younger stems quadrate to terete, evenly and more or less The range of C. torreyana extends from trans -Pecos Texas A yellow-flowered form of Chuparosa ( Justicia cali f ornica) at Rancho Santa Ana Botanic Garden, Claremont, California.

Dyschoriste decumbens growing in the Canelo Hills, Santa Cruz County, Arizona. Photo by M. Butterwick. 170 Desert Plants 5 (4) Winter 1984

eastward to southern Texas and southward into adjacent of Mexico are extremely variable with respect to most of these regions of north -central Mexico. In our region, it occurs on characters and in the absence of a thorough systematic study slopes and along arroyos in Chihuahuan Desert scrub at about of this genus, they are here considered as part of one variable 1000 to 1200 meters elevation (Fig. lc). and widely distributed species. Representative specimen examined: Texas: Presidio Co.: The species is distributed from the southwestern United Cibolo of the Rio Grande, Parry et al. 4276 (NY, US). States southward through western and west -central Mexico to Guerrero. The species was reported from New Mexico by Wooton and Standley (1915) and Martin and Hutchins (1981); both treatments cited Mearns 2037 from Guadalupe Canyon. I Dicliptera Jussieu have been unable to locate the Mearns collection although the Herbs or shrubs; calyx 5- lobed; corolla with an ampliate tube species occurs in the Arizona portion of Guadalupe Canyon and a bilabiate limb comprising an entire or emarginate upper and likely occurs in the New Mexico portion as well. Charles lip and an entire or shallowly trilobate lower lip; stamens 2, Wright collected the species in Guadalupe Canyon (Wright anthers bithecous, the thecae unequally inserted, with or 1465 at GH! and NY!) on 4 October 1851 (fide E. Shaw, in litt.) without basal appendages; placentae separating from mature but it is not known if he was in Arizona or New Mexico at the capsule walls; seeds 4 or fewer per capsule. time. In Arizona, the species occurs in the rocky soils of slopes Several hundred species have been described from temperate and washes in desert scrub and grassland habitats at elevations and tropical regions of both Old and New Worlds. from 1000 to 2000 meters (Figs. ld, 3a). Representative specimens examined: Arizona: Cochise Co.: 1. Dicliptera resupinata (Vahl) Juss. Ann. Mus. Paris 9: Guadalupe Canyon, Walker s.n. (Southwestern Research Sta., 268. 1807. Portal); Pima Co.: 3.5 mi. below Molino Basin Campground, Sta. Justicia resupinata Vahl, Enum. Pl. 1: 114. 1804. Catalina Mts., Keil 4308 (ASU); Pinal Co.: Triangle Y Camp near D. pseudoverticillaris Gray, Proc. Amer. Acad. Arts 20: 308. Oracle, Hesselberg s.n. (ARIZ); Santa Cruz Co.: Sanford Butte, 1885. Circle Z Ranch, Van Devender and Koppinger s.n. (ARIZ). D. torreyi Gray, Proc. Amer. Acad. Arts 20: 309. 1885. Diapedium torreyi (Gray) Heller, Cat. N. Amer. Pl. 7. 1898. Diapedium torreyi (Gray) Woot. & Standl. Contr. U.S. Natl. Herb. 19: 598. 1915. Dyschoriste Nees Suffrutescent herb to 6 dm tall. Stems hexagonal- ridged, Suffrutescent herbs; calyx 5- lobed; corolla with an ampliate essentially glabrous to sparsely pubescent at nodes. Leaves tube and a bilabiate to subactinomorphic, 5 -lobed limb; petiolate, the petioles to 20 mm long, the blades lanceolate to stamens 4, didynamous, anthers bithecous, the thecae equally ovate, 20 - 50 (- 80) mm long, 4 - 25 (- 35) mm wide, acute to inserted, appendaged at base; seeds 4 or fewer per capsule. subattenuate at base, acute to acuminate at apex, surfaces About 100 species have been described, primarily from the glabrous to sparsely pubescent. Flowers clustered in cymules tropics and subtropics of both Old and New Worlds. in axillary, subsessile or pedunculate cymes. Bracts subtending the cymes subulate to oblanceolate, 2 - 6 mm long. Cymules 1. Dyschoriste decumbens (Gray) Kuntze, Rev. Gen. Pl. subtended by cordate to deltate to reniform (sometimes 2: 486. 1891. basally fused) bracts, 7 - 15 mm long, 6 -13 mm wide. Bractlets Calophanes decumbens Gray, Syn. Fl. N. Amer. 2(1): 325. scariose, lance -subulate to oblanceolate, 1.5 - 3 (- 7) mm long. 1878. Calyx scariose, 2.5- 3 mm long, the lobes lance -subulate. C. oblongifolius sensu Torr. in Emory, Rep. U.S. & Mex. Corolla rose -purple with white area spotted with rose -purple Bound. Surv. 2(1): 122. 1859. pro parte. Not D. Don (1833). on upper lip, (8 -) 13 - 19 mm long, the upper lip (3.5 -) 7 - 10 mm Erect to sprawling suffrutescent herb to 3 dm tall. Younger long, emarginate, the lower lip (5 -) 8 - 10 mm long, entire. stems subquadrate (and often strongly bisulcate), pubescent Stamens (3.5 -) 8 -10 mm long, the thecae pinkish, inserted one with straight to flexuose to retrorse to ascendant -appressed above the other at filament apex. Capsules obovoid, 4 mm trichomes 0.1 - 0.5 (-1) mm long, sometimes gray -canescent. long, glabrous. Seeds 4 per capsule, reniform, 1.5 - 2 mm long, Leaves subsessile to short petiolate, the petioles to 5 mm long, testa spinose- papillate. (April - October). the blades narrowly elliptic to oblanceolate to obovate, 10 - 37 It was into the synonymy of this species that Torrey (1859) mm long, 3 - 13 mm wide, attenuate at base, acute to rounded and Gray (1878, 1880) included D. thlaspioides Nees, a species at apex, surfaces pubescent. Flowers solitary or clustered in described from southern Mexico. In the supplement to his leaf axils (to the base of plant). Bractlets usually petiolate, Synoptical Flora of North America, Gray (1886) later rejected oblanceolate to narrowly elliptic, 10 - 30 mm long, 2 - 6 mm this inclusion. Examination of a photograph of the type of D. wide, pubescent like leaves. Calyx 10 -16 mm long (at thlaspioides reveals that itisidentical with D. pringlei anthesis), accrescent in fruit (to 20 mm), pubescent like leaves, Greenman, a species also described from Morelos. It differs the lobes subulate -filiform. Corolla blue -purple, 15 - 25 mm from D. resupinata by its circular to widely elliptic cymule long, the tube ampliate above, the lobes subequal, 5 - 7.5 mm bracts and longer (3.5 - 6 mm) calyx. This treatment is similar long. Stamens in 2 basally fused pairs, the longer stamens 6 - 7 to that of Leonard in Shreve and Wiggins (1964) in which D. mm long, the shorter stamens 4.5 - 6 mm long, the thecae pseudoverticillaris was included in D. resupinata. Specimens bluish, 1.1 -1.5 mm long, with a pointed spur at the base. identified as the former taxon from Arizona usually have Capsule 10 -12 mm long, glabrous. Seeds 4 per capsule, sessile to subsessile cymes, truncate to acute, basally fused subtriangular, 3 mm long, covered with appressed, silky cymule bracts, and smaller flowers than specimens recognized trichomes (appearing glabrous when dry). (April - October). as the latter taxon. Specimens of D. resupinata from other parts The taxonomy of and keys to species of Dyschoriste are not Daniel Acanthaceae 171

very satisfying. It is evident that Kobuski (1928) recognized too or commonly in whorl -like clusters, subsessile to short - many ill- defined species in his monograph of the genus. All of petiolate, the petioles to 3 mm long, the blades lanceolate to the specimens examined from our region appear to be part of oblanceolate, 17 - 80 mm long, 4 - 23 mm wide, attenuate at the same species, D. decumbens. The relationships of this base, acute to acuminate at apex, surfaces and margin nearly species with other related species, especially D. linearis (Torr. & glabrous to sparsely pubescent. Flowers in densely bracteate Gray) Kuntze, need to be worked out in detail. In D. linearis of spikes, these usually clustered and borne on and intergrading eastern and central Texas the stems have stiff, flexuose to re- into long scaly peduncles. Peduncles often bearing clusters of curved trichomes 0.2 -1.3 mm long, mostly concentrated in two leaves in acaulescent individuals. Scales lance -subulate, 2.5 - 5 vertical lines and the leaves are mostly linear. In D. decumbens mm long, slightly overlapping one another. Bracts lance- ovate, the stems are evenly cinerous puberulent and the leaves are 4 - 6 mm long, 1.5 - 2 mm wide, 3- toothed at apex, the lateral mostly oblanceolate to obovate. Specimens of D. decumbens teeth hyaline, wing -like, the margin hyaline. Bractlets sub - from Texas and New Mexico tend to be erect in stature and scariose, lance -subulate, 3.5 - 4.5 mm long, margin hyaline often have longer trichomes (to 1 mm) whereas those from Calyx scariose, 3.5 - 5 mm long, segments 4, dissimilar, the Arizona tend to be sprawling- decumbent in stature and have anterior bidentate. Corolla blue with a white eye spotted with shorter trichomes. There is overlap, however, in both of these orange on the lower lip, 7 - 11 mm long, upper lip 1.5 - 2 mm features with respect to plants in both geographic regions. It is long, lower lip 4 - 5 mm long with the lobes divided at apex. not known whether these tendencies are part of the natural Stamens 1.5 mm long, the thecae 0.7 mm long. Capsule variability of the species or represent intergradation (caused by subconic, 3 - 4 mm long, glabrous. Seeds subconic, 0.5 - 0.7 mm hybridization) with other species of Dyschoriste. long, covered with minute projections. (April - October). The species ranges from the southwestern United States A common and widely distributed species ranging from the southward through central Mexico. In our region, it occurs on southwestern United States southward throughout western rocky slopes in grassland communities and chaparral with Mexico and Central America to South America and the West oaks, junipers, and pines at elevations from 1000 to 2350 Indies and introduced into the Old World tropics. In our region meters (Figs. le, 3b). it occurs on rocky hillsides and in washes in grasslands and Representative specimens examined: Arizona: Cochise Co.: oak woodlands at elevations from 1150 to 1650 meters (Figs. lf, Huachuca Mts., near Parker Canyon Lake, McGill et al. 213 3c, d). (ASU); Pima Co.: Ophir Gulch, 4 mi. N and 2 mi. W of Sonoita, Representative specimens examined: Arizona: Cochise Co.: Tramontano T36 (ARIZ); Santa Cruz Co.: Papago Springs Cave, ca. 2.5 mi. E of Bisbee, McGill and Keil 8540 (ASU); Pima Co.: 6 mi. S of Sonoita, Van Devender s.n. (ARIZ, ASU). New Mexico: Rincon Mts., near Vail, Thornber 7136 (ARIZ); Santa Cruz Co.: Chaves Co.: jct. Hwys. 82 and 13, W of Artesia, Higgins 10265 0.3 mi. past Harshaw jct., SE of Patagonia, Pinkava et al. 14688 (NMC); Eddy Co.: 6 mi. S of White's City, Hitchcock et al. 4323 (ASU). New Mexico: Hidalgo Co.: Maverick Spring Canyon, (DS, UC, WTU); Lincoln Co.: 5 mi. W of Lincoln, Hitchcock et Peloncillo Mts., Wahl 83 (UNM). Texas: Presidio Co.: Cienega al. 4280 (DS, UC, WTU). Texas: Brewster Co.: Sul Ross Hill, Ranch near Capote Falls, Hinckley 1700 (ARIZ). Alpine, Warnock 21465 (DS); Culberson Co.: US Hwy. 62, N of Pine Springs, 3.4 mi. SW of New Mexico line, Burgess 2388 (ARIZ); Jeff Davis Co.: Davis Mts., Ft. Davis, Ferris and Duncan 2657 (DS); Pecos Co.: Valleys, Tharp 43 -853 (CAS); Presidio Co.: Henrya Nees ca. 12 mi. S of Marfa, Correll and Wasshausen 27900 (UC); Herbs, subshrubs, or shrubs; bractlets fused along one side; Reeves Co.: Hwy. 2901 mi. E jct. Hwy. 80, Johnston 3289 (SRSC); calyx 5- lobed, one lobe conspicuously reduced in size; corolla Terrell Co.: Sanderson, Crockatt s.n. (NMC). with a slender tube and a bilabiate limb comprising an entire or emarginate upper lip and a 3 -lobed lower lip; stamens 2, anthers bithecous, the thecae equally to subequally inserted, lacking basal appendages; seeds 2 per capsule. Elytraria Michaux Fewer than 20 species occurring mostly in Mexico and Caulescent or acaulescent suffrutescent herbs; calyx 4- Central America. lobed, the anterior lobe bidentate; corolla with a cylindric tube and a bilabiate limb comprising a bibbed upper lip and a 1. Henrya insularis Nees in Benth. Bot. Voy. Sulphur 148. trilobed lower lip; stamens 2, anthers bithecous, the thecae 1844. equally inserted, lacking basal appendages; retinacula papilli- H. brevifolia Happ, Ann. Missouri Bot. Gard. 24: 547. 1937. form; seeds minute, up to 14 per capsule. Suffrutescent perennial herb to 3 dm tall. Stems viscid, more Approximately 15 species occurring primarily in the tropics or less densely pubescent with glandular trichomes 0.1 - 0.8 and subtropics of both Old and New Worlds. mm long. Leaves subsessile to petiolate, the blades ovate to elliptic, 10 - 65 mm long, 8 - 44 mm wide, rounded to acute at 1. Elytraria imbricata (Vahl) Pers. Syn. Pl. 1: 23. 1805. base, acute to rounded at apex, surfaces glandular pubescent, Justicia imbricata Vahl, Ecol. Amer. 1: 1. 1796. becoming glabrate. Inflorescence of lax spicate axes to 20 cm Verbena squamosa Jacq. Pl. Hort. Schoenbr. 1: 3. 1797. long. Bracts (linear) oblanceolate, 3 - 4.5 mm long, 0.8 - 2 mm Elytraria tridentata Vahl, Enum. Pl. 1: 107. 1804. wide, glandular. Bractlets oblanceolate, 7 -10 mm long, glandu- Thbiflora squamosa (Jacq.) Kuntze, Rev. Gen. Pl. 2: 500. 1891. lar. Calyx 1- 2 mm long. Corolla whitish with yellow and Elytraria squamosa (Jacq.) Lindau, Anal. Inst. Fisico -Geogr., reddish markings on upper lip, 10 - 13 mm long, upper lip 5 - 7 Costa Rica 8: 299. 1958. mm long, lower lip 6.5 - 9 mm long. Stamens 7 mm long, the Herb from woody caudex. Stems (if present) glabrous or very thecae 1.5 - 2 mm long. Capsule 5 - 7 mm long, glabrous or sparsely pubescent. Leaves (often absent at anthesis) alternate sparsely pubescent at apex. Seeds 2 mm in diameter, smooth to Carlowrightia linearifolia. Carlowrightia arizonica. Photo by F. Young.

Ruellia nudif lora. Stenandrium barbatum. Photo by T Van Devender. Daniel Acanthaceae 173 papillose on one side, densely pubescent with appressed inserted, unequal in size, the lowermost longer and with a trichomes on the other. (June). basal spur. Capsule 7-8 mm long, glabrous or sparsely A weedy species ranging from the southwestern United pubescent at apex. Seeds subcircular, 2.5 - 3.5 mm in diameter, States southward throughout most of Mexico to Panama. It is puberulent with apically barbed trichomes. (April - July). known only from one locality in the United States, a canyon Presently known only from western Texas and southeastern bottom in Arizona at an elevation of 1150 meters (Figs. lg, 2c,d). New Mexico, this species undoubtedly occurs in adjacent The above description has been augmented by information regions of Mexico. It occurs on limestone flats at elevations from specimens from nearby Sonora. from 1050 to 1450 meters (Fig. 1h). Representative specimen examined: Arizona: Santa Cruz Representative specimens examined: New Mexico: Eddy Co.: Parajito Mts., Sycamore Canyon, Toolin s.n. (ARIZ). Co.: Carlsbad, McKechnie 29 (MO, UNM); Texas: Pecos Co.: 22 mi. S of Ft. Stockton, Warnock and McVaugh 8707 (LL, SRSC). Justicia L. 2. Justicia warnockii Turner, Field & Lab. 19: 100. 1951. Herbs or shrubs; calyx 4 or 5- lobed; corolla with an ampliate Erect, basally branched, broom -like to globose suffrutescent tube and a bilabiate limb comprising an entire, emarginate or perennial to 40 cm tall, arising from a woody caudex. Younger bilobed upper lip and a trilobate lower lip; stamens 2, anthers stems terete- striate, strigillose (rarely only slightly so) in 2 bithecous, the thecae subequally or unequally inserted, one or vertical lines, the trichomes recurved, 0.05 - 0.20 mm long. both appendaged at base; seeds 4 or fewer per capsule. Leaves sessile, strongly ascendant, linear to narrowly oblance- More than 300 species distributed in temperate and tropical olate, 2.5 - 25 mm long, 0.4 - 1.3 (- 2) mm wide, acute at apex, regions of both Old and New Worlds. glabrous. Flowers solitary, sessile in leaf axils or sessile in the 1. Leaves sessile, linear to oblanceolate, 0.4 - 4 mm wide; axils of reduced leaves or bracts along the upper portion of the corolla 7 - 12 mm long; capsule 6.5 - 8 mm long. stem, forming a spicate axis to 8 cm long. Bractlets linear - 2. Young stems more or less evenly strigillose, the tri- subulate to filiform, 1.5 - 4.5 mm long, 0.2 - 0 4 mm wide, chomes recurved -appressed; leaves pubescent; bractlets glabrous. Calyx 4- lobed, (2 -) 3 - 4 mm long. Corolla whitish or 0.5 - 2 mm wide; lower theca 1- 1.3 mm long lavender with purplish markings in throat, 7 - 12 mm long, 1. J. wrightii pubescent on outer surface, upper lip 4 - 5.5 mm long, lower lip 2. Young stems strigillose in 2 vertical lines, the trichomes 6 mm long with lobes 2 - 4 mm long. Stamens 3.5 mm long, the recurved; leaves glabrous; bractlets 0.2 - 0.4 mm wide; thecae subparallel, unequally inserted, unequal in size, the lower theca 0.7 - 0.8 mm long 2. 1. warnockii lower longer and with a basal spur. Capsule 6.5 - 8 mm long, 1. Leaves petiolate, the blades lance -ovate to ovate to sub - glabrous. Seeds round to oval, 2 - 2.5 mm long, granulate, the orbiculate, 3 - 40 mm wide; corolla 21- 40 mm long; capsule margin fringed with glandular trichomes to0.1 mm long. 10 - 22 mm long. (December - July). 3. Calyx 4- lobed; suffrutescent herb to 4.5 dm tall; corolla Restricted to the Chihuahuan Desert region of western pinkish purple, glandular on outer surface; capsule Texas and adjacent Mexico (Coahuila and Chihuahua) where glandular 3. J. sonorae it occurs on limestone slopes in desert scrub at elevations from 3. Calyx 5- lobed; shrubs to 2 m tall; corolla red (rarely 600 to 1650 meters (Fig. 1h). yellow in J. californica), not glandular on outer surface; Representative specimens examined: Texas: Brewster Co.: capsule not glandular. Old Blue, Glass Mts., Warnock W325 (DS, F, GH, NCU, NY, 4. Stems pallid, pubescent with trichomes 0.05 - 0.10 PH, SRSC, TEX, UC); Hudspeth Co.: Quitman Mts., S of Sierra mm long; bractlets 1.5 - 4.5 mm long; corolla entirely Blanca, Warnock et al. 18061 (SRSC); Pecos Co.: ca. 25 mi. S of red (or yellow), lobes of lower lip 1 - 4 mm long; Ft. Stockton, McVaugh 10654 (DS, DUKE, ENCB, LL, MICH, capsule 16 - 22 mm long, pubescent. MO, NY, PH, SRSC, UC); Presidio Co.: 0.25 mi. N of Solitario 4. J. californica Peak, Johnston 3430 (US); Terrell Co.: along Rio Grande 4. Stems not pallid, pubescent with trichomes 0.2 -1 between Reagan Canyon and Sanderson Canyon, Warnock mm long; bractlets 5 - 12 mm long; corolla red with 15855 (SRSC). white markings on lower lip, lobes of lower lip 5 - 10 mm long; capsule 10 - 14 mm long, glabrous 3. Justicia sonorae Wasshausen, Phytologia 49: 65. 1981. 5. J. candicans Suffrutescent herb to 4.5 dm tall. Stems terete to sub - quadrate, glabrous or pubescent with eglandular, flexuose 1. Justicia wrightii Gray, Syn. Fl. N. Amer. 2: 329. 1878. trichomes 0.2 -1 mm long below and with scattered glands 0.1 Erect, basally branched, suffrutescent perennial, 8 - 15 cm -0.3 mm long above. Leaves short petiolate, the petioles to 5 tall, arising from a woody caudex. Younger stems terete- striate, mm long, the blades lance -ovate to ovate, 10 - 55 mm long, 3 -22 the ridges frequently brownish, the grooves green, more or less mm wide, acute to acuminate at apex, truncate to rounded to evenly strigillose, the trichomes recurved -appressed, 0.1 - 0.2 acute at base, surfaces pubescent. Inflorescence of axillary or mm long. Leaves sessile, linear to oblanceolate, (5 -) 10 -15 mm terminal, spicate axes to 15 cm long, these sometimes basally long, 1.5 - 4 mm wide, acute to rounded at apex, pubescent like branched, the axes densely glandular. Bracts triangular - young stems or the trichomes mostly restricted to margin. subulate to lance -subulate, 2 - 4 mm long, 1-1 5 mm wide, Flowers solitary, sessile in leaf axils. Bractlets linear -subulate glandular. Bractlets lance -subulate, 2 - 3 mm long, 0.6 - 0.8 mm to oblanceolate, 2.5 - 11 mm long, 0.5 - 2 mm wide, pubescent wide. Calyx 4- lobed, 3.5 - 5.5 mm long. Corolla pinkish purple, like leaves. Calyx 4- lobed, 2.5 - 4.5 mm long. Corolla purplish, 23 - 35 mm long, sparsely glandular on outer surface, upper lip 8.5 - 12 mm long, pubescent on outer surface, upper lip 4.5 - 6.5 6.5 - 11 mm long, lower lip 8 - 17 mm long with lobes 5 - 6 mm mm long, lower lip 4 - 6 mm long with lobes 3 - 4 mm long. long. Stamens 8 - 9 mm long, the thecae parallel to subparallel, Stamens 3 - 5 mm long, the thecae subparallel, unequally subequally inserted, 1.2 - 2.2 mm long, lacking prominent basal 174 Desert Plants 5 (4) Winter 1984

2cm

Figure 2. Diagnostic features of genera of southwestern Acanthaceae: a, flower of Anisacanthus thurberi; b, capsule and seeds of Carlowrightia serpyllifolia; c, leaf of Henrya insularis; ci, inflorescence node of H. insularis showing bracts, fused bractlets and flower bud; e, corolla of Justicia candicans; f, habit_ of Tetramerium nervosum showing dense, four -sided spikes. Daniel Acanthaceae 175

1 mm

1cm a

Figure 3.Diagnostic featuresofgeneraofsouthwestern Acanthaceae: a, cyme of Dicliptera resupinata with three cymules; b, upper portion of androecium of Dyschoriste decumbens; c, habit of Elytraria imbricata showing scaley peduncles and densely bracted spike; d, bract of E. imbricata; e, flower of Ruellia nudiflora; f, capsule and seeds of R. nudiflora; g, corolla of Siphonoglossa Iongiflora; h, habit of Stenandrium barbatum; i, two stamens of S. barbatum showing monothecous anthers. 176 Desert Plants 5 (4) Winter 1984

spurs. Capsule 10 - 12 mm long, densely glandular. Seeds 2 - 2.5 mm long, the new growth very densely pubescent. Leaves mm in diameter, densely tuberculate. (May). petiolate, the petioles to 8 mm long, the blades ovate, 13 - 39 Restricted in distribution to the southwestern United States ( -70) mm long, 7 - 30 ( -36) mm wide, truncate to rounded to and adjacent Mexico (Sonora). Known in our region from a acute at base, acute to acuminate at apex, surfaces pubescent. single locality in southern Arizona where the plant was Flowers solitary or clustered in axils of reduced upper leaves collected in a deep arroyo at 1230 meters elevation (Fig. 1h). (these sometimes reduced to lanceolate or ovate bracts). The above description has been augmented by information Bractlets linear -subulate to oblanceolate, 5 -12 mm long, 0.7 - 3 from specimens from nearby Sonora. mm wide. Calyx 5- lobed, 5 - 8 mm long. Corolla red with white Representative specimen examined: Arizona: Cochise Co.: markings on the lower lip, 25 - 37 mm long, pubescent on outer Kiper Springs, ca.Lat. 32 °03'N. Long.110 °24' W, 7lrrner surface, upper lip 9 - 16 mm long, lower lip 9 -17 mm long with 79 -77 (ARIZ). lobes 5 - 10 mm long. Stamens 15 - 16 mm long, the thecae parallel, subequally to unequally inserted, 1.5 - 2 2 mm long, the lower apiculate (sometimes obscurely so). Capsule 10 - 14 4. justicia californica( Benth.) D. Gibson, Fieldiana mm long, glabrous. Seeds subcircular, flattened, 3 - 4 mm in Botany 34: 67. 1972. diameter, tuberculate, glabrous. (December - May). Beloperone californica Benth. Bot. Voy. Sulph. 38. 1844. A widely distributed species ranging from the southwestern Jacobinia californica Nees in DC. Prodr. 11: 729. 1847. United States southward through western Mexico to Oaxaca. Sericographis californica (Benth.) Gray in Torr. in Emory, In our region it occurs along washes and on canyon slopes in Rep. U.S. & Mex. Bound. Surv. 2(1): 125. 1859. Sonoran Desert scrub at elevations from 500 to 1250 meters Erect shrub to 2 m tall. Younger stems terete, very finely and (Figs. 1h, 2e). evenly pubescent giving the stems a pallid aspect, the tri- Representative specimens examined: Arizona: Maricopa Co.: chomes 0.05 (- 0.1) mm long. Leaves (plants often leafless at 1.1 mi. SW of Port of Phoenix near Canyon Lake, Marshall 82 anthesis) petiolate, the petioles to 20 mm long, the blades (ASU); Pima Co.: main canyon N of Alamo Canyon, Ajo Mts., ovate to deltate to suborbicular, 8 - 65 mm long, 5 - 40 mm Gould and Darrow 4683 (ARIZ). wide, truncate to truncate -cuneate at base, acute at apex, surfaces pubescent. Flowers in racemose axes at branch apices, these often sparsely or densely glandular. Bracts caducous, lance -elliptic, 4 - 6 mm long, 1.5 - 2 mm wide, pubescent like Ruellia L. inflorescence axis. Bractlets subulate, 1.5 - 4.5 mm long, 0.5 - Herbs, shrubs, or trees; calyx 5- lobed; corolla usually with a 0.8 mm wide. Calyx 5- lobed, 4.5 - 8 mm long. Corolla entirely distinct tube and throat and a subactinomorphic limb of 5 lobes; red (rarely yellow), 21 - 40 mm long, pubescent on the outer stamens 4, didynamous, anthers bithecous, the thecae equally surface (occasionally with glands as well as eglandular tri- inserted, lacking basal appendages; seeds 4 to 20 per capsule. chomes), upper lip 9 - 20 mm long, lower lip 9 - 20 mm long Approximately 250 species distributed primarily in the sub- with lobes 1- 4 mm long. Stamens 15 -19 mm long, the thecae tropics and tropics of both Old and New Worlds. unequally inserted, 2 - 2 8 mm long, the lowermost with a short 1. Herb from woody caudex; leaves 20 - 170 mm long, 10 - 90 mm wide, attenuate at base; calyx (9 -) 11 - 25 mm long, the basal spur. Capsule 16 - 22 mm long, pubescent. Seeds subglobose, 2.5 - 3 5 mm in diameter, glabrous. (October - June). anterior lobes not joined for half or more of their length; A species restricted in distribution to the Sonoran Desert corolla lobes 10 - 12 mm long; capsule 12 - 22 mm long, region of the southwestern United States and northwestern glandular; seeds 3 - 4 mm long. 1 R nudiflora Mexico where it occurs on sandy or rocky soil, particularly 1. Subshrub; leaves 9 - 35 mm long, 3 - 15 mm wide, acute at along washes, in desert scrub at elevations from 100 to 1200 base; calyx 6 -11 mm long, the anterior lobes joined for half meters (Fig. 1h). or more of their length; corolla lobes 5 -10 mm long; capsule Representative specimens examined: California: Imperial 10 - 13 mm long, not glandular; seeds 2.5 - 3 mm long .. . Co.: Jacumba Mts., 3 mi. SW of Ocotillo, Holmgren and 2. R. parryi Holmgren 7552 (ASU); Riverside Co.: ca. 22 mi. E of Indio, Haller 1552 (ASU); San Diego Co.: Hwy. S -22 at W edge of 1. Ruellia nudiflora (Engelm. & Gray) Urban, Symb. Borrego Springs, Partin et al. 2758 (ASU). Arizona: Maricopa Antill. 7: 382. 1912. Co.: Scottsdale Rd., 2.5 mi. N of Bell Rd., Lehto 134 (ASU); Dipteracanthus nudi florus Engelm. & Gray, Bost. J. Nat. Mohave Co.: 3 mi. S of Hope, Norris 25 )ASU); Pima Co.: Organ Hist. 5: 229. 1845. Pipe Natl. Mon., East Loop, Pinkava et al. 9959 (ASU); Pinal Co.: R. tuberosa L. var. occidentalis Gray, Syn. Fl. N. Amer. 2(1): Sierra Estrella, Lower Reservoir, Smith S090 (ASU); Yuma Co.: 325. 1878. Tinajas Altas in Tinajas Altas Mts., Reeves et al. 5388 (ASU). R. nudiflora var. glabrata Leonard, J. Wash. Acad. Sci. 17: 518, 1927. 5. Justicia candicans (Nees) L. Benson, Tr. & Sh. Southw. R. glabrata (Leonard) Tharp & Barkley, Amer. Midl. Naturl. Des. 218. 1981. 42: 13. 1949. Adhatoda candicans Nees in DC. Prodr. 11: 396. 1847. Herb from woody caudex to 3 dm tall. Stems bisulcate- Jacobinia ovata Gray, Proc. Amer. Acad. Arts 21: 405. 1886. quadrate, sparsely pubescent with flexuose trichomes to 2 5 mm (Not Justicia ovata (Walt.) Lindau 1900). long, especially at the nodes, sometimes with a dense under - Jacobinia candicans (Nees) Benth. & Hook. ex Hook. & story of straight trichomes and glands 0.2 - 0.5 mm long. Leaves Jacks. Ind. Kew. 1: 1246. 1893. petiolate, the petioles to 50 mm long, the blades ovate to broadly Erect shrub to 1.5 m tall. Younger stems subquadrate, evenly ovate, (2 -) 3 - 17 cm long, 1- 9 cm wide, long attenuate to pubescent with flexuose to flexuose- ascending trichomes 0.2 -1 truncate- attenuate at base, rounded to subacute at apex, margin Daniel Acanthaceae 177

undulate- crisped, surfaces pubescent. Inflorescence a terminal, obovate, 9 - 25 (- 35) mm long, 3 - 15 mm wide, acute at base, thrysoid panicle with glandular axes. Bracts subtending in- acute to rounded at apex, margin entire to undulate, usually florescence branches lance -subulate, 3.5 - 9 mm long. Bractlets conspicuously ciliate, surfaces glabrous or pubescent with lance -subulate to subulate, 2- 6 mm long. Calyx (9 -) 11- 25 mm flexuose (often dendridic or malpighiaceous) trichomes to 1 long, glandular, the lobes subequal, linear, the anterior lobes not mm long. Flowers axillary, subtended by 2 bractlets. Bractlets joined for half or more of their length (as in R. parryi). Corolla leaf -like, lanceolate to elliptic to obovate, 7 -16 mm long. blue, (25 -) 30 - 50 mm long, the lobes 10 - 12 mm long. Longer Calyx 6 - 11 mm long, the lobes unequal in size, the anterior stamens 11 - 12 mm long, shorter stamens 7 - 8 mm long, the segment 2 lobed at apex, the lateral lobes often reduced in thecae 3 - 3.5 mm long. Capsule ellipsoid, 12 - 22 mm long, glan- length, the posterior lobe entire. Corolla blue, 27 - 42 mm long, dular. Seeds usually 10 or more per capsule, flat, cordate, 3 - 4 the lobes 5 -10 mm long. Longer stamens 7 - 9 mm long, shorter mm long, covered with a smooth melding of trichomes which stamens 5 - 6 mm long, the thecae 2 mm long. Capsule 10 - 13 usually form a hyaline margin, the trichomes becoming distinct mm long, glabrous or pubescent with eglandular trichomes. on wetting. (April - September). Seeds 6 or more) per capsule, flat, 2.5 - 3 mm long, pubescent Gray (1878, 1880) considered these plants to belong to R. with appressed trichomes. (March - October). tuberosa L. and described them as variety occidentalis of that Distributed in the Chihuahuan Desert region of the south- species in 1878, noting that the Arizona specimens were western United States and adjacent Mexico where it occurs on glabrate forms. Leonard (1927) accepted R. nudiflora as a limestone ledges and in arroyo beds in desert scrub and juniper morphologically variable species closely related to R. tuberosa. chaparral communities at elevations from 500 to 1800 meters In order to emphasize its diversity, he recognized nine varieties (Fig. 1 i). in R. nudiflora. Plants in our region were treated as R. nudiflora Representative specimens examined: New Mexico: Dona var. glabrata, distinguished by its mostly large and glabrate Ana Co.: Rattlesnake Ridge, Organ Mts., Worthington 6049 leaves and glandular -pilosulous inflorescences, and R. nudi- (ARIZ, NMC, UTEP); Eddy Co.: Vs mi. SSE of Elevator Tower, floravar. nudiflora, with smaller leaves and glandular - Dole 84 (UC). Texas: Brewster Co.: near abandoned Wax Factory puberulent inflorescences. In their colorful treatment of on Rio Grande at mouth of Big Canyon, McVaugh 7797 (DS, Ruellia in Texas, Tharp and Barkley (1949) raised most of TEX); Culberson Co.: 18 mi. N of Van Horn, Sierra Diablo Mts., Leonard's varieties to specific rank. It is not clear at the present Van Devender s.n. (ARIZ); Hudspeth Co.: 4 mi. NE of Indian time whether the minor differences among the taxa recognized Hot Springs, Quitman Mts., Waterfall 4850 (CAS); Pecos Co.: 25 in this assemblage are properly reflective of species, infra - mi. S of Ft. Stockton, Madera Mts., Correll et al. 29697 (LL, UC); specific taxa, or variation within a widespread species. Until a Presidio Co.: Livingston Hills, 4 mi. S of Shaffer, Van Devender thorough revision of this complex has been completed, a et al. s.n. (ARIZ); Terrell Co.: 1 mi. E of Sanderson, Warnock conservative approach will likely suffice for treating these 11891 (LL). plants. When the relationships of the paniculate species of Ruellia of North and Central America have been studied in detail, I believe that the plants from the southwestern United States will ultimately be considered a part of R. tuberosa or R. Siphonoglossa Oersted paniculata L.) where Asa Gray placed them over a hundred Suffrutescent herbs: calyx 4 or 5- lobed; corolla with an years ago. elongate, cylindric tube and a bilabiate limb comprising an As here treated, R. nudiflora is a widely distributed and entire or emarginate upper lip and a 3 -lobed lower lip; stamens morphologically variable species ranging from Arizona to 2, anthers bithecous, the thecae unequally inserted, one or Lousiana (although not reported from New Mexico), southward both minutely appendaged at base; seeds 4 or fewer per throughout much of Mexico and Central America to Costa capsule. Rica. In our region it occurs in sandy washes and roadside About 25 species distributed in the New World and ditches in desert scrub and desert grassland at elevations from southern Africa. 450 to 1350 meters (Figs. li, 3e, f). 1. Cauline trichomes 0.1 - 0 2 mm long; corolla white, 33 - 55 Representative specimens examined: Arizona: Cochise Co.: mm long. 1. S. longiflora San Bernadino Ranch, Mearns 737 (DS); Pima Co.: 6 mi. S of 1. Cauline trichomes 0.2 - 1.5 mm long; corolla pink, 17 - 32 Tucson, Gould 2645 (CAS); Santa Cruz Co.: between Sopori mm long 2. S. pilosella School and Arivaca, Tate 270 (ASU). Texas: Brewster Co.: NE side of Bullis Range, vic. of Tank 11 on Bullis Gap Ranch, Butterwick and Lott 3655 (TEX); Pecos Co.: 15.5 mi. W of 1. Siphonoglossa longiflora (Torn.) Gray, Syn. Fl. N. Bakersfield at Tunis Spring, Correll and Wasshausen 27961 Amer. 2(1): 328. 1878. (LL); Terrell Co.: Mile Long Canyon at Langtry, Skiles 4 (SRSC). Adhatoda longiflora Torr. in Emory, Rep. U.S. & Mex. Bound. Surv. 2(1): 125. 1859. Erect subshrub to 3.5 (-5) dm tall. Younger stems sub - 2. Ruellia parryi Gray, Syn. Fl. N. Amer. 2(1): 326. 1878. quadrate, striate, evenly pubescent with retrorse- appressed Dipteracanthus suffruticosus Torr. in Emory, Rep. U.S. & trichomes 0.1- 0.2 mm long. Leaves subsessile to petiolate, the Mex. Bound. Surv. 2(1): 122. 1859. Not R. suffruticosus petioles to 7 mm long, the blades linear -lanceolate to lanceo- Roxb. 1814. late to elliptic to ovate, 5 - 70 mm long, 2 - 8 (- 14) mm wide, Erect subshrub to 5 dm tall. Younger stems bisulcate- acute to subattenuate at base, acute to acuminate to falcate at quadrate, glabrous or evenly pubescent with retrorse trichomes apex, pubescent like stems. Flowers solitary or clustered in 0.1 - 0.2 mm long. Leaves petiolate, the petioles to 7 mm long, axils of upper leaves. Bractlets linear to lance- elliptic, 4 - 9 (- 20) the blades (ovate) lance- elliptic to elliptic to oblanceolate to mm long, 0.5 -1.5 (- 3) mm wide. Calyx 5- lobed, 4.5 - 6 ( -12) mm 178 Desert Plants 5 (4) Winter 1984 long, the lobes linear to lance -elliptic. Corolla white, 33 - 55 Stenandrium Nees mm long, tube 28 - 43 mm long, 1-1 5 mm in diameter, upper Caulescent or acaulescent perennial herbs; calyx 5- lobed; lip 5 - 7 mm long, lower lip 6 - 10 mm long with lobes 4 - 8 mm corolla with a cylindric -ampliate tube and usually a subactino- long. Stamens 4 - 7 mm long, the thecae 1 -1.5 mm long, basally morphic, 5- parted limb; stamens 4, monothecous; seeds 4 or spurred. Capsule 8 -10 mm long, glabrous. Seeds subcircular, 2 - fewer per capsule. 2.5 mm in diameter, tuberculate. (March - December). Approximately 20 species distributed in the tropics and Occurring in the southwestern United States and north- subtropics of the New World. western Mexico where it grows in rocky washes and arroyos in desert scrub at elevations from 1000 to 1350 meters (Figs. lj, 3g). The species has been reported from the Chihuahuan Desert of trans -Pecos Texas (Lott and Butterwick, 1980) 1. Stenandrium barbatum Torr. & Gray, Pacific Rail. however the specimen (Butterwick and Lott 3872) has been Rep. (Pope's Explor.) 2: 168. 1855. misplaced at TEX. Gerardia barbata (Torr. & Gray) Blake, Contr. Gray Herb. Representative specimens examined: Arizona: Graham Co.: 52: 100. 1917. Dry Canyon of Gila River, ca. 2 - 3 mi. downstream from Bonita Dwarf perennial herb to 10 cm tall from a stout woody rhi- Creek, McGill 2312 (ASU); Maricopa Co.: ca. 3 mi. NE of zome. Leaves clustered at ground level, sessile or short petio- Apache Trail in Superstition Mts., Daniel and Butterwick 3191 late, the petioles to 5 (- 25) mm long, the blades oblanceolate to (ASU); Pima Co.: 6 mi. W jct. Speedway and Silverbell in Tucson spatulate, 8 - 45 mm long, 2 - 5 j- 9) mm wide, acute at apex, Mts., Daniel 159 (ASU); Pinal Co.: 0.5 mi. S of Superior on Hwy. tapering- attenuate at base, pubescent with a sparse to dense 177, Wood s.n. (ASU); Santa Cruz Co.: Agua Caliente Canyon, understory of erect or bent trichomes 0.1- 0.2 mm long and an Santa Rita Mts., Kaiser 1061 (ARIZ); Yavapai Co.: Lion Peak, overstory (sometimes restricted to the margin) of flexuose tri - Weaver Mts., Butterwick and Hill yard 6894 (ASU). chomes 1- 4 mm long. Flowers axillary in leafy -bracteate spikes. Bracts oblanceolate to obovate to elliptic, 7 - 21 mm long, 2 - 4 mm wide, pubescent like leaves. Bractlets subulate, 1.5 - 6 mm long, 0.3 - 0.6 mm wide. Calyx 4 -8 mm long, the lobes 2. Siphonoglossa pilosella (Nees) Torr. in Emory, Rep. subequal, lance -subulate. Corolla pinkish purple with white U.S. & Mex. Bound. Surv. 2(1): 124. 1859. streaks on lower lip, 13 - 21 mm long, the lobes subequal, 4 - 9 Monechma pilosella Nees in DC. Prodr. 11: 412. 1847. mm long. Stamens 1.5 - 2 mm long, the thecae 1.5 mm long. Adhatoda dipteracantha Nees in DC. Prodr. 11: 396. 1847. Capsule 9 - 14 mm long, glabrous (rarely pubescent). Seeds 3 - S. dipteracantha (Nees) Heller, Contr. Herb. Franklin & 5 5 mm long, densely pubescent with long, stiff, golden tri - Marshall Coll. 1: 95. 1895. chomes with recoiled branches. (March - October). Erect to spreading herbs to 2 dm tall from a woody rhizome. A species restricted to the Chihuahuan Desert of southern Stems bisulcate- quadrate, pubescent with evenly disposed (or New Mexico, western Texas, and adjacent portions of Chihua- mostly restricted to 2 lines) flexuose or retrorse trichomes 0.2 - hua and Coahuila where it occurs on limestone slopes and 1.5 mm long. Leaves sessile or subsessile, the petioles to 5 mm arroyo gravel in desert associations up to pinyon -juniper long, the blades ovate to elliptic to obovate, 8 - 35 mm long, 4 - communities at elevations from 750 to 1350 meters (Figs. 20 mm wide, cuneate to acute at base, rounded to acute at apex, lk,3h, i). upper surface pubescent or nearly glabrous, lower surface Representative specimens examined: New Mexico: Chaves usually pubescent. Flowers axillary. Bractlets leaf -like, oblan- Co.: ca. 2 mi. W of Roswell, Hinckley and Smith 4374 (SRSC); ceolate to elliptic to ovate, 8 - 12 mm long, 1.5 - 6 mm wide. Doria Ana Co.: 6 mi. W of El Paso, Hanson s.n. (TEX); Eddy Co.: Calyx 5- (rarely 4 -) lobed, 5 - 8 mm long, the lobes lance - 2 mi. W of Carlsbad, Crutchfield 1337 (LL); Lea Co.: Monu- subulate. Corolla pink with white eye on lower lip, 17 - 32 mm ment, Castetter 70907 (UNM); Lincoln Co.: 10 mi. NW of long, upper lip 3 -10 mm long, lower lip 5 -12 mm long. Stamens Riverside, Goodman and Waterfall 4958 (CH); Otero Co.: San 5 - 7 mm long, the thecae 1.3 -1 6 mm long, the lowermost with Andres Canyon, Sacramento Mts., Van Devender and Betan- a short spur. Capsule 7 - 9 mm long, glabrous. Seeds cordate, 2.5 - court s.n. (ARIZ); Sierra Co.: Elephant Butte Dam, Nelson 6122 3.5 mm long, tuberculate. (March - November). (UNM). Texas: Brewster Co.: along Rio Grande at Hot Springs, A species occurring from southeastern New Mexico east- Warnock 13937 (TEX); Culberson Co.: San Antonio Peak, ward through trans -Pecos Texas to eastern and southern Texas Sierra Tinaja Pinta, Correll and Rollins 23873 (ENCB, LL); El and southward into adjacent regions of Mexico. In our region it Paso Co.: ca. 3 mi. W of El Paso in Franklin Mts., Warnock grows on rocky ledges and slopes among brush or boulders 8368 (LL, SRSC); Hudspeth Co.: 12 mi. NW Indian Hot Springs, mostly in grassland communities at elevations from 350 to Turner 374 (LL, SRSC); Jeff Davis Co.: W of Chispa summit, 2150 meters (Fig. lj). Johnston et al. 10684 (LL); Pecos Co.: ca. 25 mi. S of Ft. Representative specimens examined: New Mexico: Eddy Stockton, Sierra Madera, McVaugh 7914 (ASU, SRSC, TEX); Co.: Walnut Canyon, Guadalupe Mts., McKechnie s.n. (UNM). Presidio Co.: 2 mi. S of Shafter, Warnock 46642 (SRSC); Reeves Texas: Brewster Co.: ca. 16 mi. E of Alpine, Warnock 46571 Co.: 16 mi. NW of Toyahvale, Correll and Correll 38527 (US); Culberson Co.: Apache Mts., 4 mi. N of Kent, Warnock (ENCB, LL, TEX, UC); Terrell Co.: between Langtry and 19740 (SRSC); Jeff Davis Co.: ca. 17 mi. N of Ft. Davis, Correll Sanderson, McKelvey 1926 (A). and Hanson 29844 (US); Pecos Co.: 4 mi. W of Longfellow, Turner 555 (SRSC); Presidio Co.: Capote Canyon, ca. 25 mi. W T7etramerium Nees of Marfa, Hinckley 1501 (ARIZ); Terrell Co.: 4 mi. E of Subshrubs or shrubs; inflorescence usually conspicuously Sanderson, Hitchcock and Stanford 6824 (DS). 4- sided; calyx 4 or 5- lobed; corolla with a slender, apically Daniel Acanthaceae 179 ampliate tube and a bilabiate limb comprising an entire to Puercos River, Schott s.n. (F). Texas: Presidio Co.: Musgrave emarginate upper lip and a 3 -lobed lower lip; stamens 2, Canyon, Sierra Tierra Vieja, Hinckley 1912 (ARIZ, TEX). anthers bithecous, the thecae equally or subequally inserted, lacking basal appendages; seeds 4 or fewer per capsule. Approximately 15 species distributed in North, Central, and Acknowledgements South America. I am grateful for the courtesies extended by the curators of the following herbaria: A, ARIZ, ASU, CAS, DES, DS, DUKE, ENCB, F, GH, K, LA, LL, MICH, MO, NCU, NMC, NY, PH, RSA, SMU, SRSC, Southwestern Research Station (Portal, TEX, UC, UNM, US, UTEP, 1. Tetramerium nervosum Nees in Benth. Bot. Voy. WTU. The following people were especially helpful in one way or another: D. Pinkava, B. Turner, E Almeda, R. Worthington, M. Sulph. 148. 1844. Butterwick, E. Shaw, T. Van Devender, G. Marrs, and R. Hilsenbeck. T. hispidum Nees in DC. Prodr. 11: 468. 1847. The illustrations were prepared by Mark Mohlenbrock. T. nervosum Nees in Benth. var. hispidum Torr. in Emory, Rep. U.S. & Mex. Bound. Surv. 2(1): 125. 1859. Erect to sprawling subshrub to 3 dm tall. Younger stems terete to subquadrate, usually pubescent with a mixture of Literature Cited flexuose to retrorse trichomes 0.2 - 0.5 mm long, concentrated Correll, D. S. and M. C. Johnston. 1970. Manual of the Vascular Plants in 2 lines, and straight to flexuose, more or less evenly of Texas. Texas Research Foundation. Renner. disposed trichomes 0.5 -1 mm long (sometimes absent), rarely Gray, A. 1878. Synoptical Flora of North America. Vol. 2 Ivison and Co. with glands to 0.4 mm long as well. Leaves petiolate, the New York. petioles to 10 (- 20) mm long, the blades narrowly lanceolate to Gray, A. 1880. Acanthaceae. In: Whitney, J. D. Geological Survey of California: Botany. Vol. 1, 2nd ed. Little, Brown, and Co. Boston. ovate, 10 - 45 (- 70) mm long, 2 - 16 (- 32) mm wide, acute to Gray, A. 1886. Synoptical Flora of North America. Vol. 2 Ivison and Co. rounded at base, acute at apex, surfaces pubescent. Flowers in New York. densely bracteate, 4 -sided apical spikes. Bracts lance- ovate, 7 - Kearney, T. H., R. H. Peebles, and Collaborators. 1960. Arizona Flora. 15 mm long, 3.5 - 5 mm wide, falcate -mucronate at apex, the 2nd ed. University of California Press, Berkeley. surfaces strongly nerved, the margin conspicuously hirsute Kobuski, C. E. 1928. A monograph of the American species of the with trichomes to 1.5 mm long. Bractlets subulate, 2.5 - 5 mm genus Dyschoriste. Ann. Missouri Bot. Gard. 15:9 - 91. long. Calyx 4 -lobed (in ours), 2.5 - 4.5 mm long, the lobes Leonard, E. C. 1927. Ruellia tuberosa and a few of its close relatives. J. subulate. Corolla cream with a blue eye streaked with purple Wash. Acad. Sci. 17:509 - 520. veins on upper lip, 12 - 17 mm long, upper lip 6 - 8 mm long, Leonard, E. C. 1964. Acanthaceae. In: Shreve, E and I. Wiggins. lobes of lower lip 7 - 9 mm long, the lower -central lobe keel - Vegetation and Flora of the Sonoran Desert Vol. 2. Stanford University Press. Stanford. -1.1 mm long. like. Stamens 5 - 5.5 mm long, the thecae 1 Long, R. W. 1970. The genera of Acanthaceae in the southeastern Capsule 4 - 5.5 mm long, pubescent. Seeds suboval, 1.5 - 2 mm United States. J. Arnold Arbor. 51:257 -309. long, tuberculate. (April - October). Lott, E. and M. Butterwick. 1980. Notes on the flora of the Chinati A weedy and widely distributed species occurring from the Mountains, Presidio County, Texas. Sida 8:348 -351. southwestern United States southward throughout much of Martin, W. C. and C. R. Hutchins. 1981. A Flora of New Mexico. Vol. 2. Mexico and Central America to northern South America and R. Gantner Verlag Kommanditgesellschaft. Vaduz. the Galapagos Islands. In our region it occurs on rocky slopes, Munz, P. A. 1959. A California Flora. University of California Press. in washes and along arroyos in Sonoran and Chihuahuan Berkeley. Desert scrub, in grassland associations, and in disturbed places Tharp, B. C. and E. A. Barkley. 1949. The genus Ruellia in Texas. Amer. at elevations from 350 to 1650 meters (Figs. 11, 2f). Midi. Natur. 42:1 - 86. Torrey, J. 1859. Acanthaceae. In: Emory, W H. Report on the United Representative specimens examined: Arizona: Cochise Co.: States and Mexican Boundary Survey. Vol. 2. U.S. Dept. of San Bernadino Ranch, ca. 17 mi. E of Douglas, Daniel and Marrs Interior. Washington. 1807 (ASU); Graham Co.: 10 mi. N of Klondyke, Darrow s.n. Wasshausen, D. C. 1966. Acanthaceae. In: Lundell, C. L. Flora of Texas. (ARIZ); Pima Co.: I -19 and Palo Prado Rd., N of Nogales, Lehto Vol. 1. Texas Research Foundation. Renner. 20283 (ASU); Santa Cruz Co.: N outskirts of Carmen, Keil Wooten, E. O. and P. C. Standley. 1915. Flora of New Mexico. Contr. U.S. 11060 (ASU). New Mexico: Socorro Co.: Bravo del Norte near Natl. Herb. 19:1 - 794. 180 Desert Plants 5 (4) Winter 1984

Introduction. New Plant Records The Gulf Coast mountains form an interrupted band of low pediments along the length of western Sonora. The geology of the coastal area between Puerto Lobos and Bahia Kino has From the been studied and mapped (Gastil and Krummenacher 1976, Gastil et al. 1977), but the remaining region is still poorly Sonoran Desert' known. Gentry( 1972) suggested that most of the coastal ranges were islands or maritime headlands during portions of the Upper Tertiary (2 -20 million years ago). He summarized the probable physiographic development of the area and mapped a probable Miocene shoreline of the Gulf of California. George Yatskievych The Sierra del Viejo is located at about 30 °20'N latitude and Department of Biology 112 °20'W longitude, about 40 km southwest of Caborca, Indiana University Sonora. It is a narrow north -south trending range a little over and 30 km long. Elevation of the coastal plain at the base of the mountains is about 300 m and the highest point is 1020 m, at Pierre C. Fischer the summit of Cerro del Viejo. Climatic records are available Tucson, Arizona from La Union, at the southern end of the range (Hastings 1964). Average temperature was 21.6 °C, with extremes of 31.1 °C in August and 11.6 °C in January (1958 -1962). Annual rainfall averaged about 200 mm, with the highest monthly means in August (72.5mm) and January (38.1 mm) The mountains lack any permanent surface water. The Sierra del Viejo is distinguished from most other mountain ranges in the low desert of western Sonora by its relatively large areas of Late Precambrian or Cambrian lime- stone (cf. Gastil and Krummenacher 1976, Gastil et al. 1977). The range is at the northeastern boundary of the areas included in the above -cited paper and map and the remaining geologic features have not been thoroughly studied. We observed that the remainder of the range is primarily granite, with smaller areas of basalt and metamorphic formations at the southern end. The endemic Agave species mentioned above grow only on the limestone, as do many of the plants reported in this article. The vegetation of the Sierra del Viejo has been included in the Lower Colorado Valley Subdivision of the Sonoran Desert (sensu Shreve 1951) by Brown and Lowe (1980), but includes The vegetation and flora of the Sonoran Desert are among many elements more typical of the Central Gulf Coast the most thoroughly documented of the arid portions of North Subdivision. The igneous and sedimentary slopes have the America. The climate and relative accessibility of the area same dominant plants; Cercidium microphyllum (Foothills have attracted many botanists and the landmark studies Paloverde), Mimosa laxiflora, Larrea tridentata (Creosotebush), resulting from their efforts, too numerous to list here (see Simmondsia chinensis (Jojoba), and Fouquieria splendens Shreve and Wiggins 1964, and Kearney and Peebles 1960 for (Ocotillo). The granitic slopes are sparsely covered with a partial bibliographies) are a testament to their achievements. greater variety of arborescent species, including Eysenhardtia In an area covering over 310,000 square km (Shreve 1951) it is orthocarpa (Kidneywood) and Prosopis velutina (Velvet Mes- not, however, surprising that some less -known localities quite). The limestone slopes effect more of an open appearance, should exist, which might harbor plant species not previously with scattered patches of Bursera microphylla (Elephant Tree) known to exist there. For example, H.S. Gentry (1972) described and Jatropha cuneata (Limberbush) interspersed with open two very distinctive Sonoran Desert species of Agave (A. zebra areas dominated by Opuntia bigelovii (Teddy -bear Cholla), and A. pelona) from localities in the mountains near the Gulf Echinocereus engelmannii (Engelmann Hedgehog), and Tiqui- of California. The plant records reported here were encoun- lia canescens (Oreja del Perro). The limestone summits and tered during visits to observe these endemic century plants in ridges are a patchwork of scrubby areas dominated by such a small range of mountains, the Sierra del Viejo. plants as Dodonea viscosa (Hopbush), Lycium berlandieri (Wolfberry), and Calliandra eriophylla (Fairy- duster) and very open "pavement- like" areas with only occasional bunchgrasses and small cacti. The minor elements of the flora are diverse ' Much of this paper resulted from discussions with Raymond Turner, and more distinct for each substrate type. Tony Burgess, Thomas Van Devender, Laurence Toolin, and Allan Zimmerman, whose insights and ideas are greatly appreciated. In The Sierra del Viejo is not well known botanically. It was addition, thanks are due to Charles T Mason, Jr. and Rebecca Eiber of apparently overlooked by most early collectors and few the University of Arizona Herbarium for their help and cooperation. specimens have reached herbaria. Gentry and associates A limestone hillside in the Sierra del Viejo, Sonora. Prominent plants are Ocotillo (Fouquieria splendens), Elephant Tree (Bursera microphylla), Limber Bush (latropha cuneata) and Agave zebra.

,. ;ti.

View northward from the Sierra del Viejo. The coastal plain is periodically broken by low mountains. 182 Desert Plants 5 (4) Winter 1984

CACTACEAE

ENSENADA Ancistrocactus uncinatus (Galeotti) L. Benson. Yatskie- 1-4 vych & Fischer 82 -20. This is a westward range extension of SONOVTA 100 km over 400 km from the closest known populations in southern SAN FELIPE New Mexico and Chihuahua (Benson 1982). It represents the NOGALES CANANEA first record for Sonora and for the Sonoran Desert for this

limestone -dwelling cactus, which is widespread in the Chi- EL ROSARIO huahuan Desert. The plants are tentatively assigned to var. LIBERTAD uncinatus on the basis of their generally fewer radial spines MOCTEZUMA PUNTA and the shape of the petaloids. This and var. wrightii (Engle- PRIETA mann) L. Benson do not appear to be well separable and the HERMOSILLO Sonoran plants are somewhat intermediate between the two. The species is relatively rare in the Sierra del Viejo, occurring

28° GUAYMAS on steep limestone slopes.

112° CIUDAD s` SANTA OBREGON ROSALIA Echinocactus horizonthalonius Lemaire var. nich-

MULEGE olii L. Benson. Yatskievych & Fischer 82 -21. This species has ALAMOS; not previously been reported from Sonora. The type variety is COMONDU restricted to the Chihuahuan Desert in New Mexico, Texas, and northeastern Mexico, while E. horizonthalonius var. nicholii has previously been reported in the Sonoran Desert from the Waterman and Vekol Mountains of southern Arizona (Benson 1982, and T. R. Van Devender, pers. comm.). Our collection consists of a single immature plant assigned to var. nicholii on the basis of its consistently five radial spines. LA PAZ Additional specimens need to be collected to determine if var. horizonthalonius (with 6 -7 radial spines) is also present in the Sierra del Viejo. The speciesis very uncommon in the mountains and is restricted to a few limestone ridgetops.

Map of northwestern Mexico showing Sonora and Baja Echinocereus scopulorum Britton & Rose. Yatskievych California. The location of the Sierra del Viejo is indicated by a & Fischer 82.17. A duplicate of this collection was determined large asterisk by Allan D. Zimmerman, University of Texas at Austin. The species is part of a confusing group of rainbow cacti that visited the range several times between 1951 and 1966. In 1980 includes E. pectinatus (Schweidweiler) Engelmann and its and 1983 R. M. Turner and coworkers made collections in the varieties. Our collection represents a northward range exten- area. M. Dimmitt and associates collected in the Sierra del sion of about 350 km for the species, which was previously Viejo in early 1983. known from Guaymas southward along the coast to northern We visited the Sierra del Viejo in 1981 and 1982. Because Sinaloa (Shreve and Wiggins 1964). In the Sierra del Viejo the the range is almost entirely privately owned it is riddled plants are scattered in crevices on steep limestone slopes and with numerous old gold, silver, and lead mines) our access can be locally common on some south -facing exposures. has thus far been limited to the northern half. Further exploration in other portions and in nearby mountains may Mammillaria lasiacantha Engelmann. Yatskievych & yield further discoveries. Fischer 82 -16. The population in the Sierra del Viejo represents The purpose of this paper is to detail nine new distributional the first record for Sonora and for the Sonoran Desert. The records for the Sonoran Desert from collections made by remaining range of the species is in the Chihuahuan Desert Turner et al., and by us in the Sierra del Viejo. Within the and adjacent grasslands, in New Mexico, Texas, and north- mountain range, specific localities for each species are not eastern Mexico, with an unconfirmed report from a grassland given here to protect particularly the cacti from possible locale in southeastern Arizona (see Benson 1982, for discus- overcollection. Voucher specimens cited are accessioned in sion). At our station, this cactus is nearly restricted to flat open the herbarium at the University of Arizona (ARIZ). Plants are limestone ridgetops with gravelly pavement -like substrate. It listed alphabetically, by family. can be locally common, but is easily overlooked because the small white nearly flat- topped plants blend very well with the surrounding rocks. ANACARDIACEAE Rhus kearneyi Barkley ssp. kearneyi. Turner 80 -10. This collection from the Sierra del Viejo represents the first main- LEGUMINOSAE land Sonoran record for this rare xerophytic shrub, previously Cassia goldmannii Rose. Turner 80 -1; Burgess 5751, 5764; known from the low hot mountains of southwestern Arizona Bowers & McLaughlin 1935. The Sierra del Viejo populations and eastern Baja California (Moran 1969). It is to be looked for represent the only mainland Sonoran records for this shrub, in other mountains of northwestern Sonora. In the Sierra del which is otherwise confined to mountains of Baja California Viejo, the plants are uncommon in limestone ravines. Sur. In the Sierra del Viejo the plants occur on both limestone Yatskievych and Fischer New Plant Records 183

Ancistrocactus uncinatus in the Sierra del Viejo.

and granite slopes and form widely scattered stands. Within a Sonora, are usually referable to E. hypomalaca Standley, rather stand they can become locally common. than E. cordata. In the Sierra del Viejo, the species is uncommon and widely scattered on lower slopes and in washes. LOASACEAE Eucnide cordata (Kellogg) Kellogg ex Curan. Felger & Gentry 7906; Burgess 5754, 5766. This species is common in POLYPODIACEAE (sensu lato) Baja California and on several of the Gulf islands, but the only Notholaena jonesii Maxon. Burgess 5759; Yatskievych & previous reports from mainland Sonora are from the vicinity of Fischer 82 -12, 82 -23. These specimens represent the first Guaymas (Waterfall 1959, Thompson and Ernst 1967). Plants records of this species from Mexico, a range extension of about from the mountains adjacent to the Sonoran Desert, in eastern 300 km to the southwest from the closest known population, 184 Desert Plants 5 (4) Winter 1984

Mammillaria lasiacantha in the Sierra del Viejo.

in the Waterman Mountains of southern Arizona. The dimin- Van Devender and Spaulding 1979), theories concerning utive plants are very uncommon in crevices of steep limestone species migrations cannot be thoroughly substantiated. Exami- slopes and are generally confined to the relative shelter of nation of the present -day ranges of plant species can, however, narrow ravines and talus. provide insight into the phytogeographic processes which account for these distributions and is thus important for both SCROPHULARIACEAE the formation and the support of theories concerning the Galveziajuncea (Bentham) Ball. Burgess 5753. This species different patterns of species migrations. ranges nearly the length of Baja California, but has not Ancistrocactus uncinatus, Echinocactus horizonthalonius, previously been reported from mainland Sonora. In the Sierra and Mammillaria lasiacantha represent species that are wide- del Viejo, plants are uncommon on both granite and limestone spread in the Chihuahuan Desert, but are uncommon in the substrates, on upper slopes and ridgetops. Plants from the Sonoran Desert, present there in a very few, apparently Sierra del Viejo are var. juncea. Previously unreported Sonoran relictual populations. Formation of this type of disjunction collections from Sierra Bacha, Punta Cirio, south of Libertad must have followed migration either across the Sierra Madre (Burgess 5715; Phillips 7517; Van Devender & Kearns s.n.) and Occidental (which separates the two deserts in Mexico) or from nearby Cerro Tepoca (Fise s.n.) are apparently var. around its northern edge (in southern Arizona and New pubescens (Brandegee) I. M. Johnston. Mexico). In either case, judging from the climates at present - day. localities, this probably occurred during a previous Discussion. interglacial period, when temperatures in the intervening The distributional records detailed above illustrate several areas were relatively high and rainfall was relatively depressed. disjunctional patterns and provide circumstantial evidence Fragmentation of the distribution would have followed with for the expansion and contraction of distributional limits for the onset of the next glaciation, as much of the area became plant species over time. While some of the species, such as too cool and wet for the plants to survive. Notholaena jonesii, are apparently adapted for long range The repeated advance and retreat of Pleistocene glaciers dispersal, it seems more probable that particularly the cacti also influenced the north -south migrations of plant species (as arrived in the Sierra del Viejo by more gradual migration along summarized by Benson 1982). Echinocereus scopulorum, which an expanding distributional boundary and were isolated there grows primarily in southern Sonora and Sinaloa, undoubtedly when a changing climate caused all nearby populations to migrated northward into the Sierra del Viejo during an become extinct. interglacial thermal maximum. By contrast, Notholaena In the absence of more direct evidence, such as from plant jonesii, whose primary distribution is in the southwestern remains in ancient pack rat middens (numerous studies, e.g., United States, may have migrated southward into Mexico Yatskievych and Fischer New Plant Records 185

An excavated flowering specimen of Mammillaria lasiacantha. during a more pluvial glacial time. North -south migration also Literature Cited. accounts for the presence of Echinocactus horizonthalonius in Benson, Lyman. 1982. The Cacti of the United States and Canada. both Arizona and Sonora. The fact that all of these western Stanford Univ. Press, Stanford, CA. populations are apparently var. nicholii suggests that the Brown, David E. and Charles H. Lowe. 1980. Biotic Communities of the species migrated from the Chihuahuan Desert region westward Southwest (1:1,000,000 scale map). U.S. Dept. Agriculture Rocky Mountain Forest and Range Experiment Station General Technical and differentiated into var. nichollii, with subsequent forma- Report RM -78. tion of the present -day latitudinal disjunction. Gastil, R. Gordon and Daniel Krummenacher. 1977. Reconnaissance The occurrence in mainland Sonora of plants primarily geology of coastal Sonora between Puerto Lobos and Bahia Kino. restricted to Baja California has long been recognized. Shreve Geol. Soc. Amer. Bull. 88:189 -198. Gastil, R. Gordon, Daniel Krummenacher, and students at San Diego ( 1961 ) documented the similarity between the vegetation of State Univ. Reconnaissance geologic map of coastal Sonora the two sides of the Gulf of California in the Central Gulf bewteen Puerto Lobos and Bahia King (1:150,000 map). Geol. Soc. Coast Subdivision of the Sonoran Desert, but also pointed out Amer. Map Chart Series MC -16. the distinctness of the plant associations along each shore. Gentry, Howard Scott. 1972. The Agave Family in Sonora. U.S. Dept. Galvezia juncea, Cassia goldmannii, and Eucnide cordata Agriculture Handbook 399:1 -195. Hastings, James Rodney, ed. 1964. Climatological data for Sonora and represent species showing trans -Gulf disjunctions. Eucnide northern Sinaloa. Univ. of Arizona Institute of Atmospheric cordata differs from the others in its presence on many of the Physics Technical Reports on Meteorology and Climatology of Arid islands in the Gulf of California. It seems reasonable to suggest Regions 15:1 -152. that this species crossed the Gulf via a pattern of "island - Kearney, Thomas H., Robert H. Peebles, and collaborators. 1960. hopping". This pattern of migration does not, however, explain Arizona Flora, second ed., with Supplement by John Thomas Howell, Elizabeth McClintock, and collaborators. Univ. of Cali- disjuctions involving the other two species. Galvezia juncea fornia Press, Berkeley, CA. and Cassia goldmannii are not commonly found on any of the Moran, Reid. 1969. Twelve new dicots from Baja California. Trans. San Gulf islands. These plants probably followed a pattern of Diego Society Nat. History 15:265 -295. migration around the head of the Gulf of California during a Shreve, Forrest. 1951. Vegetation of the Sonoran Desert. Carnegie Inst. Washington Publ. 591. 192 pp. previous period of glaciation, when rainfall (particularly in Shreve, Forrest and Ira L. Wiggins. 1964. Vegetation and Flora of the winter) was higher and temperatures were cooler in areas that Sonoran Desert, 2 vol. Stanford Univ. Press, Stanford, CA. are currently reckoned as among the hottest and driest in Thompson, Henry J. and Wallace R. Ernst. 1967. Floral biology and North America. The present -day distribution of Rhus kearneyi systematics of Eucnide (Loasaceae). J. Arnold Arb. 48:56 -88. is probably also due to this type of migrational pattern, but the Van Devender, Thomas R. and W. Geoffrey Spaulding. 1979. Develop- ment of vegetation and climate in the southwestern United States. rarity of this species makes it unwise to theorize on the Science 204:701 -710. direction of migration involved. Waterfall, U. T. 1959. A revision of Eucnide. Rhodora 61:231 -243. 186 Desert Plants 5 (4) Winter 1984

continued phology seems to have been shaped by a survival strategy to from page 160 cope with drying winds and winter drought in southern thorn scrub situations, a number of species have been able to spread out in spring). Another problem relates to the uncertainty of north through the Sonoran Desert into habitat where the same leaf production. Plants remaining leafless for extended periods morphology has adaptive value in a somewhat different of time would have difficulty maintaining an acceptable situation. To the north, the life form grows in winter -cold, carbon budget. For this reason, some species which might usually riparian, locations. In contrast to southern thorn scrub otherwise be classified here have developed further adaptive situations, the northern habitat often has abundant winter features which compensate and place them in or toward other rain. But being winter- deciduous, the life form is not adapted categories. For example, Chuparosa ( Justicia californica) and to exploit this resource. various species of spurge (Euphorbia xanti, E. colletioides) can A careful examination of the northern habitat reveals that achieve a positive carbon balance during stressful periods by the life form has exploited sites which 1) have significant cold carrying out a limited amount of photosynthesis in the stem. air drainage in winter, 2) have thunderstorms which provide Thus, during unfavorable periods they may act essentially like high averages for summer soil moisture but which "skip over " green- stemmed leafless perennials -one of the most success- a percentage of sites each year, 3) sometimes have excessive ful life forms of the Sonoran Desert. soil moisture and a resulting problem with root -rot fungi. The Examples in the drought- deciduous large- leaved perennial winter- deciduous characteristic of the life form has allowed it category are Plumeria (P. acutifolia) and various species of latro- to invade relatively cold habitats where Ironwood or Palo pha. In the latter genus some species have thickish stems and Verde are at a disadvantage or entirely absent. At these (often tend toward an intermediate condition between this life form riparian)sites, competition is usually with Cottonwood, and that of the drought- deciduous sarcocaulescent perennial. Willow, Ash, Walnut or other winter- deciduous broad -leaved trees. Due to the "skip over" phenomenon of summer thunder- Green -Stemmed Microphyllous Perennials storms, there are numerous sites where the broad -leaved forms This life form is highly flexible. When soil moisture is favor- are at a disadvantage or entirely absent. This is where able the plants are covered with foliage and are capable of a Mesquite or other microphyllous forms seem to have come in. considerable amount of photosynthesis in both leaf and stem. Associated with Mesquite is the soil fungus "Texas Root Rot" Resistance to hot, dry winds results from the microphyllous (Phymatotrichum omnivorum) which thrives when soil mois- condition. With decreasing moisture there is a tendency to ture is in excess. Although Mesquite appears to be resistant, drop more and more leaves until with extreme drought) the the fungus kills a broad spectrum of broad -leaved trees and plants are entirely leafless. In some species, if drought persists, shrubs. Mesquite and Acacia have dramatically invaded many whole branches may die and fall to favorably alter the water of the upper reaches of the Sonoran Desert in historic time budget. In Palo Verde this is referred to as "self- pruning." alone and have spread into the Upper Sonoran Life Zone as Plants in this category have an advantage over the super- well. The pods are eaten by cattle, germination improving by ficially similar Mesquite and other winter- deciduous micro - the seeds passing through the digestive tract (due to the hard phyllous perennials in that the carbon balance can be kept impervious seed coats being eaten away by the stomach acids). favorable by the ability to photosynthesize any time of year. New plants quickly spring up where spread by cattle. It has They also have an advantage over Plumeria and Jatropha or been suggested that the prehistoric megafuna of the Sonoran other drought- deciduous large -leaved perennials in being Desert may have very quickly spread this life form from one better able to cope with drying winds and in being able to riparian site to another. photosynthesize more quickly when seasonal drought ends Sonoran Desert examples of this life form are Mesquite and soil moisture is renewed. (Prosopis), Catclaw (Acacia greggii), Sweet Acacia (A. far - The best Sonoran Desert examples of this life form are the nesiana), and Desert Ferntree (Lysiloma thornberi). various species of Palo Verde or Palo Brea (Cercidium micro - phyllum, C. floridum, C. sonorae, C. praecox) and Jerusalem Winter -Deciduous Broad -Leaved Perennials Thorn (Parkinsonia aculeata). A transition toward the leafless With the exception of the hydrophytes, plants of this life green- stemmed life form is seen in the Desert Smoke Tree form are the least xerophytic of any in the Sonoran Desert. (Dalea spinosa). Although this species does produce leaves, They grow only in situations having good soil moisture - they are usually absent from large mature woody individuals. where water enters the desert from adjacent mountains or Some green- stemmed microphyllous species, though usually where extremely heavy seasonal precipitation occurs. Within not thought of as being drought- deciduous, tend to be much the life form are two kinds of species in the Sonoran Desert. leafier during periods of summer rain than during the re- One group is related to species of the temperate deciduous mainder of the year. Examples are Graythorn (Zizyphus forest outside the desert. The other group is of tropical obtusifolia), Rush Broom (Bebbia juncea), Desert Broom (Bac- derivation. charis sarothroides), and species of Rhatany (Krameria). The temperate species tend to occupy sites in the Sonoran Desert in which the habitat factors approach those of the tem- Winter -Deciduous Microphyllous Perennials perate deciduous forest most closely except that freezing is not The strategy in this group is to forego a closely regulated as severe. In this group of species the winter -deciduous nature carbon budget and the advantages of a green stem (both is clearly carried over from previous adaptation to dormancy important in the superficially similar Palo Verde) in favor of a periods of extreme cold elsewhere. Species in the tropical group high photosynthetic rate sustained by ample groundwater and are related to plants of the west coast of Mexico which show sun. This is the life form of the thorn scrub vegetation so adaptations to summer rain and winter drought. Their winter - common south of the Sonoran Desert. Although the mor- deciduous nature seems based more on genetic adaptation to Yatskievych and Fischer New Plant Records 187

Representative drought- deciduous large- leaved perennial: Lomboy (jatropha cinerea) at Tres Virgenes, near San Ignacio, Baja California del Sur. Photo by Kent Newland. In this experimental set -up, data was recorded relative to the physiological ecology of a winter - deciduous broad -leaved perennial. The scientist on the right is the late Fred Gibson, managing director of the Boyce Thompson Southwestern Arboretum at the time.

such dry winter situations than to freezing weather. Some are free -floating in deep water, never having roots Representatives of the temperate group are Walnut (juglans extending to the soil. Others are rooted into the mud of major), Ash (Fraxinus velutina), Willow (Salix gooddingii) and shallow water. Hydrophytes are characterized by thin leaves Cottonwood (Populus fremontii). Examples of the tropical and rot -resistant roots and stems. Often there are air chambers group are Trumpet Tree (Tabebuia palmeri), Palo Santo (Ipo- in the stems and leaves which not only provide buoyancy but maea arborescens) and Pochote (Ceiba acuminata). also store carbon dioxide to enable photosynthesis to occur when the plants are inundated. Parasites Occasionally it has been claimed that hydrophytes do not Although parasites come in a wide array of shapes and sizes, grow in the desert. Adherents to this viewpoint would claim they all demonstrate the same strategy for survival -to attach that wherever water exists there is no desert. For example, the to another life form, to drain energy from it, and to generally numerous desert water -holes, seeps and springs would not be live at the expense of the unwilling host. A physical feature considered part of the desert itself. But on the other hand, if unifying parasitic plants is the presence of haustoria, vascular there were no water in the desert at all, life would be impos- attachments which tap the food and water supplies of the host. sible. Water is an extremely valuable commodity in the Parasites in the Sonoran Desert range from Dodder (Cuscuta) desert. Most authorities agree that the term "desert" refers to a and Mistletoe (Phoradendron) which attach to the stems of geographic region where desert conditions prevail. By this their hosts to Broomrape (Orobanche) and Sand Root (Am- definition it is a mistake to restrict discussion of a desert only mobroma) which attach to the roots of their hosts. There are to the most xeric elements because the interactions of the also "hemi- parasites" like Owl's Clover (Orthocarpus) and organisms with each other do not allow it. Indeed, many Indian Paint Brush (Castilleja) which are capable of photo- desert birds and mammals rely on hydrophytes and riparian synthesis but also extract nutrients from host plants. plants for food. Desert -dwellers often refer to hydrophytes and Phoradendron villosum, the mistletoe which parasitizes near -hydrophytes as "phraeatophytes," a term designating Ash and Cottonwood, has thick, leathery (sclerophyll) leaves. plants which use too much water. Such plants transpire huge Phoradendron cali f ornicum, the mistletoe which parasitizes tonnages of water in the Sonoran Desert daily as vapor put Palo Verde and other microphyllous legume trees, is char- into the atmosphere. There is a large literature on phraeato- acterized by total leaflessness. Dodder (Cuscuta) spreads as a phytes in deserts because such plants compete with man in vine over its host plant. wasting water. Sonoran Desert hydrophytes include Monkeyflower (Mimu- lus), Watercress (Rorippa nasturtium -aquaticum), Batamote Hydrophytes (Baccharis glutinosa), Arrow -weed (Pluchea sericea), and These are plants which are adapted to growing in water. Willow (Salix gooddingii). Representative parasite: Broomrape (Orobanche Representative hydrophyte: Scarlet Monkey - ludoviciana) at King Canyon near Tucson, Arizona. Photo Flower (Mimulus cardinalis). Photo courtesy of Arizona - courtesy of Arizona -Sonora Desert Museum. Al Morgan, Sonora Desert Museum. Al Morgan, photographer. photographer.

Representative winter- deciduous broad -leaved perennials: Cottonwood (Populus fremontii) and Ash (Fraxinus velutina) growing along Queen Creek at the Boyce Thompson Southwestern Arboretum. Photo by Carol D. Crosswhite. Representative halophyte: Desert Holly (Atriplex hymenolytra) cultivated at the Boyce Thompson Southwestern Arboretum. Photo by Frank S. Crosswhite.

Halophytes Blumer, J. C. 1909. Observations on cacti in cultivation. Plant World These are plants which grow in salty and often highly 12:162 -164. alkaline situations. Halophytes show a wide variety of adapta- Cabrera, A. L. 1955. Latin America. In: Plant ecology, reviews of research. Arid Zone Research 6:77 -113. Unesco. Paris. tions to tolerate salt, the most uniform of which is a complex Cain, S. A. 1950. Life -forms and phytoclimate. Botanical Review osmoregulatory system. Saltcedar (Tamarix) actually has salt 16:1 -32. glands which excrete salt to modify the water which it utilizes. Crosswhite, F S. and Crosswhite, C. D., 1982. The Sonoran Desert. pp. Halophytes are rather common in desert situations because of 163 -320 in: G. L. Bender, Reference Handbook on the Deserts of North America. Greenwood Press. Westport, Ct. rapid evaporation due to extremely high temperatures and Cunningham, G. L. and Strain, B. R. 1969. An ecological significance of drying winds: as water evaporates it leaves salt behind. As seasonal leaf variability in a desert shrub. Ecology 50:400 -408. evaporation proceeds, saltiness increases as a given amount of Dechel, W. C.; Strain, B. R.; and Odening, W. R. 1972. Tissue water salt dissolved in a large amount of water remains dissolved in a potential, photosynthesis, C14- labelled photosynthate utilization, relatively small amount of water. and growth in the desert shrub Larrea divaricata Cay. Ecol. Monogr. 42:127 -141. When rocks of the earth's crust break down to form soil, Hull, H. M.; Shellhorn, S. J.; and Saunier, R. E. 1971. Variations in various products of physical and chemical degradation come cresosotebush (Larrea divaricata) epidermis. J. Ariz. Acad. Sci. together to form salts. Since salts dissolve readily in water they 6:196 -205. are constantly being flushed from the land surface into the MacDougal, D. T. 1903. Some aspects of desert vegetation. Plant World 6:249 -257. world's oceans. In desert regions, however, where a large McGinnies, W. G. 1968. Vegetation of desert environments. pp. 381- amount of the natural rainfall evaporates before it can reach 566 in W. G. McGinnies, B. J. Goldman and P. Paylore, Deserts of the the sea, soils may become rather salty. World. University of Arizona Press. Tucson. Halophytes in the Sonoran Desert include Saltbush (Atri- Raunkiaer, C. 1905.Types biologiques pour la géographie botanique. Académie Royale des Sciences et des Lettres de Danemark, Bulletin plex), Quelite Salado (Suaeda), Yerba Reuma (Frankenia pal- 5:347 -437. meri), Iodine Bush (Allenrolfea), and Saltcedar (Tamarix). Raunkiaer, C. 1934. The Life Forms of Plants and Statistical Plant Geography. Clarendon Press. Oxford. 632 pp. Raunkiaer, C. 1937. Plant Life Forms. Clarendon Press. Oxford. 104 pp. Shreve, F. 1942. The desert vegetation of North America. Botanical References Cited Review 8:195 -246. Adamson, R. S.1939. The classification of life -forms of plants. Shreve, F. 1951. Vegetation of the Sonoran Desert. Carnegie Institution Botanical Review 5:546 -561. of Washington. Washington, D. C. Al -Ani, H. A.; Strain, B. R.; and Mooney, H. A. 1972. The physiological Walter, H. 1931. Die Hydratur der Pflanze und ihre Physiologischö- ecology of diverse populations of the desert shrub Simmondsia kologische Bedeutung (Untersuchungen uber den Osmotischen chinensis. J. Ecology 60:4 -57. Wert). Fisher. Jena. A definitive source for both taxonomic and 41L, economic facts!

"Agaves are unique in the whole plant kingdom," observes Howard Gentry, "not merely because of their succulent character but because of a special role they have played in the indigenous civilizations in North America." Long a source of food, beverage, fiber, and even medicine, perhaps the full potential of these plants has yet to be realized. This extensive volume does more than address the uses to which agaves have been put by man. Each of 136 species native to continental North America is discussed in a separate essay covering taxonomic description, distinguishing features, distribution and habitat, vernacular names, horticultural notes, and of course known uses. Twenty generic groupings of the species facilitate comparison, while geographic groups further aid in identification. An abundance of line drawings, 670 pages, 7 x 10 photographs, and distribution maps makes the book even featuring more useful for field research. 268 photographs 166 line drawings 38 maps October 1982 $49.50 Agaves AGAVES CONTINENTAL of nó Continental North America by Howard Scott Gentry ARD scan'GENTRY

UNIVERSITY OF ARIZONA PRESS 1615 E. Speedway/ Tucson, AZ 85719 The Boyce Thompson Southwestern Arboretum near Superior, Arizona displays a wealth of cacti in greenhouses and on the grounds. The various forms, shapes, sizes and colors represent various adaptations of one basic life form successful in the desert because of crassulacean acid metabolism.

Crassulacean Acid Metabolism. The various types of cacti all proportion to the degree of coolness. During warm tropical nights have one overwhelmingly important adaptation which enables them relatively little CO, could be fixed to fuel metabolism. The shallow to succeed under harsh desert conditions. This adaptation maifests roots absorb water from even the lightest of rains, the water being itself both anatomically and physiologically. Anatomically the sign of quickly stored in the succulent gel with carbon -enriched acids. Such the syndrome is the succulent condition; physiologically the indication water -filled tissues are extremely susceptible to freeze damage and are is "crassulacean acid metabolism." When plant scientists finally at considerable disadvantage during temperate -zone winters. In the became aware of the chemistry and functioning of succulent plants daytime the sun shines through the waxy epidermis, providing crucial they began to relate physiology to internal anatomy and external warmth to split CO2 chemically from the acids (and to vaporize H20), morphology. Soon it became apparent that the succulent life form was while providing light to photosynthetically combine captive CO, with exploiting diurnal changes in temperature and osmotic pressure to captive H2O to form sugar, the fuel which drives metabolism. Due to forge a new way of living. the thick waxy epidermis (and stomata closing through the daytime), There were several clues and questions which eventually led to an the plant body literally acts as a "pressure cooker" to hasten the understanding of "succulentism" as a life form:1) Although the chemical reactions and to keep the captive CO2 and water vapor from photosynthesis of plants is based on the coming together of CO, and escaping! This manner of functioning is totally different from that of H2O in the presence of chlorophyll in sunlight, the stomata of cacti other plants. A broadleaf tree, for example, to bring water up from the and other succulents open only at night so that CO, enters the leaf in depths of the ground, must transpire water vapor through the stomata darkness! How could photosynthesis occur? 2) The plants are rooted in to the atmosphere, creating an evaporative engine which pulls an a shallow soil layer on the surface of the desert. This inhospitable layer unbroken chain of water molecules up through the vascular tissue would seem the least desirable for plant roots because it dries out so from the roots eventually to the leaves to be used in photosynthesis. In quickly and completely following precipitation. Why don't the roots such a "normal" plant the CO2 constantly enters the leaves through the extend deeper to moist soil? 3) Cacti and other succulents have a thick stomata throughout the day as some water vapor is transpired out to waxy epidermal covering and the stomata close in the daytime to very the surrounding air. But a cactus or other succulent would quickly effectively isolate and insulate the internal tissues. How does lose its precious store of water if it transpired in this manner. Without transpiration occur? 4) The inner tissues are gel -like, containing large significant transpiration (due to closing of stomata in daytime), cacti amounts of water and a veritable pool of organic acids (bitter when and succulents rely on osmotic pressure and capillarity to draw water tasted). Why is the gel so acid? 5) The life form is successful under a up from the roots into the plant body, mechanisms incompatible with (subtropical) regime of hot days and cool nights with little or no winter raising moisture from great depths of soil. freezing. Why is it relatively unsuccessful under fully tropical or In the case of succulentism, the "goodness of fit" of the various pieces temperate conditions? of the puzzle make a coherent whole which is so perfect as to suggest The various answers and other bits of information proved to be that other desert life forms must also have comparable secrets which pieces of a fantastic jig -saw puzzle which have now carefully been we have not yet unlocked! The present issue of Desert Plants attempts fitted together. The organic acids have proven to be in a temperature - to delve into the functioning of certain life forms of the Sonoran dependent equilibrium with carbon dioxide, being upgraded by CO2 Desert. With regard to many of these we are as yet at a very imperfect when cool, but giving up CO2 when warm. Thus, with stomata opening state of knowledge. In several cases we have enough pieces to the at night, carbon content of the succulent tissues increases in jig -saw puzzle to see that a marvelous picture will someday emerge.