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Home , Acorus calamus, Aerenchyma, Bidens connata, Bidens vulgata, Carex blanda, Cicuta bulbifera

Aquatic and Patricia A. Dalton and of the Arnold Alejandro Novelo R. Arboretum Illustrations by Amy Storey

In contrast to terrestrial plants, aquatic and (Lobelia siphilitica), waterweed (Elodea wetland plants are not permanent in their canadensls/, two pondweeds ( habitats. Year after year we find that a foliosus and P. epihydrus~, and even a rare that may be abundant m one year aquatic in the primrose family (Hottoma m- disappears in another. Because of fluctuating flata). Today not one of these plants can be water levels, artificial destruction, pollu- found. Yet Palmer observed that even then tion, and modification of the surface soil, the number of native species was decreasing some species are unable to survive. Such dis- rapidly in proportion to that of encroaching turbances also create new habitats that cultivated trees and shrubs allow alien species to become naturalized. The term aquatic usually refers to As a result, we receive only glimpses of the plants having a life cycle that revolves complex relationships between the plants around water, being either completely sub- and their environment. It is important, merged, emergent, or floating. Many defim- therefore, to document the flora of an area tions of this term exist, however, as these over time, so that changes brought about by plants exhibit a wide range of morphological human modifications and environmental expression, and a clear distinction between factors may be measured. wet and dry environments is often impossi- The aquatic and wetland plants in the Ar- ble to achieve. Furthermore, in many areas boretum are unique in that their status has there are seasonal fluctuations of the water been assessed from time to time throughout table; for example, plants growing in dry the history of the institution. E. J. Palmer’s soils most of the year may be flooded during Spontaneous Flora of the Arnold Ar- the rainy season, and habitats with standing boretum, the first account of wild plants in water may dry out during the summer the Arboretum, was written in 1930. Palmer, months. who was a botanist on the staff of the Ar- are transitional areas between boretum, recorded the following species as aquatic and terrestrial environments, where growing m the meadow or in shallow water the water table is usually at or just below the at that time: calamus ( calamus/,), surface or where the land is covered by shal- bur-reed ( eurycarpum St. low water. At the the John’s-wort (Hypericum majus), cardinal most familiar wetland type is what is termed (Lobelia cardinahs great blue lobelia . Though the water table may 8

be slightly below the surface of the ground, sitional zone is the attached floating- the soil on these sites receives a continuous stemmed hydrophytes. These plants are at- supply of moisture. The vegetation includes tached to the substrate with the stems float- grasses, which are usually the dominant ing on the surface of the water, for example, species, sedges, and other plants such false loosestrife (Ludwigia) and some grass as smartweeds, arrow-heads, rushes, and genera. The may be emerging or float- cat-tails. Like most meadows, these areas ing, and the reproductive organs are usually would soon grow to trees and shrubs if they aerial. were not mowed annually in the fall. The last group is comprised of plants One of the most familiar features of growing in the deeper waters offshore. This aquatic vegetation is the zonation or se- includes the free-floating hydrophytes and quence of life forms, which is typically re- the free submerged hydrophytes. Free- peated in lakes, , canals, , and floating hydrophytes are unattached to the slow-moving rivers that are not drastically substrate, and their vegetative and repro- disturbed by humans. An illustration of this ductive organs float on the surface of the wa- zonation may be found on page 9. The ter, for example, duckweed (Lemna), water- emergent plants occupying the shoreline, or (Azolla), and water-hyacinth (Eichor- marginal zones, are first in this sequence and nia). Free submerged hydrophytes are plants are called attached emergent hydrophytes. unattached to the substrate, with the vegeta- These plants are attached to the substrate tive organs submerged and the reproductive with a portion of the stem arising from the organs emerging from the water. An exam- water, for example, cat-tails (Typha), ins ple of this is the bladderwort (Utricularia). (Iris), and pickerelweed ~Pontederia/. All the reproductive parts of the plant are above water. The next group in the sequence is those plants found growing between the shoreline and the deeper waters, the transitional zone. This group includes three life forms. The at- tached floating-leaved hydrophytes are first. These plants are attached to the substrate, with the leaves floating on the surface of the water, for example, water-lilies () and water-chestnuts (Trapa). The reproduc- tive organs may be floating or emerging. The attached submerged hydrophytes are sec- Life forms of aquatic plants. Left to right: ond. These plants are attached to the sub- Attached floatmg-stemmed hydrophyte (Lud- strate, and their vegetative parts are fully wigia~; free-floating hydrophyte (LemnaIi , free submerged, for submerged hydrophyte /Utncularia/; example, pondweed attached submerged hydrophyte /Potamageton/; (Potamogeton) and naiads (Najas/. The re- attached floating-leaved hydrophyte /Nymphaea/; productive parts may be submerged, floating, and attached emergent hydrophytes (Typha and or emerging. The third life form in the tran- Iris). 9 10

Broad-leaved Cat-tail: Typha latifolia lands that are too wet for other purposes. Cat-tail Family: Although little is known of its pulping qual- ities, methods of using the stems and leaves Cat-tail stands are a familiar sight through- of this plant are now being developed for out New roadside England, especially along paper-making. In the 18th and 19th cen- ditches and other disturbed wetland areas. In turies papermaking from cat-tails was a fact, the presence of cat-tails is often an in- flourishing industry in New York. Today the dication of as this is disturbance, species soft fiber is used in making mats, chair seats, the first to invade areas af- among adversely baskets, and other woven articles. fected by human activities. Cat-tails are tol- erant of a wide range of soil and water condi- tions and spread rapidly, often as much as 177 feet per year. Whole colonies may be up- rooted by water, wind, and animals, but Water-Plantain: Alisma subcordatum loose parts are carried to other bodies of Water-Plantain Family: Alismataceae water and become firmly established. The species is found over most of temperate The Alisma, in the family Alis- , , and eastern Asia. At mataceae (water plantams), was once of the Arboretum it can be seen in extensive great interest to botanists because it was stands in the meadow, along the margins of thought to be among the most primitive the three ponds, and on the banks of Bussey (plants having a single Brook. ), perhaps derived from aquatic dicotyle- A rooted, emergent hydrophytic plant, dons (plants having 2 seed leaves) best rep- this cat-tail grows up to 7 feet tall, with long, resented in the . How- stout submerged in the mud. The ever, evidence now shows that the Alis- light green leaves, which are erect, flat, mataceae are not primitive but highly spe- linear, and elongate, emerge from the water, cialized, with complex vegetative organiza- with a sheath closely enveloping the lower tion and floral development. Two species, part of the stem. The is a Alisma triviale andAlisma subcordatum, dense, cyclindrical spike, which has two are frequent on , in shallow waters portions, the upper containing the staminate of the ponds, and along Bussey Brook at the and the lower the pistillate flowers. Arnold Arboretum. The genus Alisma is The staminate flowers are ephemeral, while widely distributed throughout the United the pistillate flowers are persistent, with the States. fruit forming a dark brown, showy spike Water-plantain is an emergent hydrophyt- with hairy fruits up to 7 inches long and 2 ic plant with a cluster of long-petioled inches wide. These small single-seeded leaves surrounding the flower stalk. The fruits are produced in great numbers, up to leaves exhibit a wide variety of patterns and 20,000 to 70,000 per inflorescence. Typha is may be slender to broadly ovate. In rare in- wind pollinated and produces powdery stances the leaves are reduced to ribbonlike pollen. structures. The inflorescence is a large pani- Cat-tail can be cultivated as a fiber crop on cle with whorled branches bearing many 11I

Common Cat-Tail (Typha latifoha~I 12z

Water-Plantam ~Ahsma subcordatum) 13

small perfect flowers. The 3 broadly ovate Brook. It blooms from July through Sep- green are persistent and surround the tember. 3 small pinkish . Six and ap- This rooted, emergent hydrophytic plant proximately 10 to 25 pistils are arranged in a reaches 3 feet tall, with its submerged in ring on a flattened receptacle. The fruit of the mud. Duck-potato is a perennial that Alisma is an achene (dry, indehiscent, and overwinters by means of tubers. In late sum- one-seeded) with one or two grooves and a mer and early fall the stolons (elongate under- minute ascending beak. It has been stated ground stems) begin to produce terminal tu- that dormancy in the is due to the bers by an enlargement of the 2 or more short, mechanical restraint of the seed coat, which thickened intemodes next to the apical bud. allows the seeds to lie in water for years The tubers, now full of , are enclosed by without losing their viability. scale leaves and are deeply embedded in the Water-plantain secretes nectar, which soil. may attract such pollinators as flies and Like many aquatic plants, the duck- short-tongued bees. Unlike those of most potato, or arrow-head, exhibits many bewil- plants, the anthers in all the flowers dehisce dering morphological variations within vari- at about the same time, so pollen is available ous habitats, which for the duck-potato may for only a short period of time. include margins, lakes, swamps, and sluggish streams. The emergent, long petioles produce leaves that are generally arrow-shaped but may also be linear to ovate in form. Accompanying the leaves is an Duck-Potato: Sagittaria latifolia inflorescence composed of whorls of flowers Water-Plantain Family: Alismataceae that are usually arranged with the upper A botanist on the Lewis and Clark Expedition whorls staminate and the lower pistillate. observed an Indian woman collecting duck- There may be as many as 10 or more whorls potato (Saglttaria latifolia) from a canoe per inflorescence, and each flower is com- near the mouth of the Columbia River. The posed of 3 sepals and 3 showy white petals. woman would paddle out to where the water The fruits are in a dense head and are was breast high and use her toes to separate beaked. the tuber from the root. The tuber, about the size of a hen’s egg, would then float to the top, and the woman would throw it into a basket in the canoe. Although duck-potato is no longer eaten by human beings, it is of con- siderable value to wildlife and has been planted as a source of both food and shelter for wildfowl. The species ranges from Nova Scotia and British Columbia southward to Mexico. At the Arnold Arboretum it is common m the meadow and along pond margins and Bussey 14

Duck-Potato (Sagittana latifoha) 15s

Arrow-Arum: Pickerelweed: Pontederia cordata Arum Family: Pickerelweed Family: Pontederiaceae

The starchy root from which arrow-arum Pontederia is a small genus of aquatic plants (Peltandra virginica) grows was once eaten distributed throughout subtropical and by the Indians in , who called the temperate regions of North America. Pon- plant tuckaho. The root, which is extremely tederia cordata, pickerelweed, is restricted acrid and poisonous, was steamed m a to the eastern provinces of and the heated pit, covered over with earth, and left eastern to midwestern , with undisturbed for a day or two. This process its greatest concentration along the Atlantic broke down the crystals of calcium oxalate coastal plain and the Great Lakes Region. It that make the plant poisonous. The dried grows in saltwater along the coast roots were then ground up into meal. and in fresh water inland. It is common in Arrow-arum ranges from to , the ponds at the Arnold Arboretum and north throughout New England and into blooms from July to late September. Canada. At the Arboretum it grows in shal- This rooted, emergent hydrophytic plant low waters in the three ponds and along Bus- has rhizomes that are short, thick, and pros- sey Brook. trate in the mud. Reproduction occurs when This rooted, emergent hydrophytic plant rhizomes break and form new growths. The is produced from a stout, spongy rootstock. long-petioled leaves, up to 9 inches long and The leaves are quite variable in form but are 5 inches wide, are quite variable in form but usually arrow shaped with wavy margins. are parallel veined and usually heart-shaped. The leaves of arrow-arum may be easily con- The showy inflorescence is a spike of deep fused with those of duck-potato (Sagittaria purplish blue flowers, each having a yellow latifolia). However, the leaves of arrow- spot at the base of the upper perianth lobes. arum have only 3 distmct nerves, while Pickerelweed is one of the few plants that those in the duck-potato have more than 3. exhibit three flower forms of the same The inflorescence is similar in appearance to species. The three forms are: plants with such familiar members of the arum family as three medium stamens, three long stamens, skunk cabbage (Symplocarpus foetidus) and and a short style; plants with three short wild calla (Calla palustris). The long, green stamens, three long stamens, and a medium spathe almost conceals the whitish clublike style; plants with flowers having three short spadix, which is completely covered with stamens, three medium stamens, and a many minute flowers. The basal portion of long style. The three forms ensure cross- the spadix contains the pistillate or female pollination. Pollen transfer from a to flowers, while the upper portion contains a pistil of equivalent length appears to be the staminate or male flowers. Green berries more productive of seeds than pollen trans- are produced in the fall. This plant has an fer from a stamen to a pistil of unequal efficient way of planting its seeds. The stalk, length. The fruits are small, winged with covered by the leathery green spathe, curves several longitudinal ridges, and very buoy- and grows downward, driving the seeds into ant. Travel by water is thought to be this the soft mud. plant’s main mode of long-distance dispersal. 166

Arrow-Arum ~Peltandra vmgmica) 177

Pickerelweed (Pontedena cordata)/ 18

Common Blue Flag: Iris versicolor Yellow Iris: Iris Family: Iris Family: Iridaceae The to The common blue flag /Iris versicolor) is a lovely yellow iris is believed be the member of the family of plants aptly named source of the fleur-de-lis of the French heral- after Iris, the Greek goddess of the rainbow. dic shield, which dates from the 12th cen- This beautiful blue-violet flower has 3 broad tury. recurved sepals (the falls) boldly veined with The Iris genus is found throughout the green, white, and yellow, and 3 smaller temperate regions of the northern hemi- erect, slender petals (the standards). sphere. It contains 300 species, of which 10 This species is a gregarious one. Plants are are aquatic. The iris was rarely found as isolated individuals, and yellow introduced to Canada from Eurasia single colonies of up to several hundred have and Africa and escaped from been observed. The range of the blue flag in cultivation, spreading to freshwater wet- North America coincides with the northern lands to such an extent as to give the appear- ance of a native It is also believed to range of the white pine (Pinus strobus),), plant. comprising New England, New York, have been cultivated in this country during Pennsylvania, northern Ontario, and north- Colonial times. The first record of an es- dates ern Michigan. The plant prefers moist soils capee from 1911 in Newfoundland. By but also grows in standing water. The blue 1915 the species was found in Nova Scotia, flag blooms from May through June at the and it eventually became established in Arboretum and is common in the meadow British Columbia, , Ontario, and and along pond margins and Bussey Brook. Prince Edward Island. This rooted, emergent hydrophytic plant Yellow iris has become an aggressive weed in has stems up to 3 feet long. The long, narrow parts of the eastern United States from leaves are pale green to grayish and sheathed Massachusetts south to Virginia and west to at the base. In the absence of the flowers, the Wisconsin. It is common in the meadow and leaves of the blue flag can easily be confused along pond margins and Bussey Brook at the with those of the cat-tail (Typha latifolia). Arnold Arboretum and blooms from May to The blue-flag leaves are straight and tightly July. A the folded, while those of the cat-tail are flat and rooted, emergent hydrophytic plant, iris to 3 feet from slightly twisted at the top. yellow grows tall, arising The greenish fruit of the blue flag is 3 long, creeping, stout rhizomes. The leaves often form from the water angled and up to 11/z inches long and 1 inch clumps emerging wide. The seeds float readily and travel by and are dark green, slender, up to 1 inch water, spreading themselves along lake and wide, and parallel veined. The flower stalk is river margins. erect, about as tall as the leaves, and pro- duces 1 to 2 flowers at the apex in the axils of the small upper leaves. The 2 involucral bracts are shorter than the showy, bright yel- low flowers, which are composed of 3 outer recurved sepals and 3 yellow inner petals, slender, to 4 inches long. The sepals have 19

Common Blue Flag (Ins versicolor) 20

I. Yellow Ins (Ins pseudacorus/ 21

delicate brown lines or flecks at the base and flowers are trimorphous. The petals are on the claw. The fruit capsule is bright green bright magenta and crinkly. The number of and often lustrous. It is bluntly 3-angled and stamens is usually twice the number of pet- contains somewhat round corky seeds. als. The stamens vary in length and are ar- ranged in two whorls. The fruit is a capsule.

Fragrant Water-Lily: Nymphaea Loosestrife: Decodon odorata verticillatus Water-Lily Family: Loosestrife Family: Growing in stagnant and muddy water, it bursts so and fair to the and so sweet to the The genus Decodon is monotypic, that is, it up pure eye scent, as if to show us what purity and sweetness includes only one species, Decodon verticil- reside in and can be extracted from the slime and latus, swamp loosestrife. This species grows muck of earth. only in the United States, ranging from Lou- David Thoreau isiana to Florida and northwards to Min- Henry Summer: From the journal nesota . material has and been of Henry Damd Thoreau found in Asia and Europe. At the Arboretum the swamp loosestrife grows in the pond The buds of the fragrant water-lily (Nym- near the lilacs and blooms from July to Oc- phaea odorata) open in early morning, ex- tober. posing the spectacular white, waxy flowers, Swamp loosestrife, or water willow, as it which float on the surface of the water. is also called, has a unique way of reproduc- Some flowers fold up their petals during the ing. The stems, which can reach 6 to 8 feet early afternoon, while others remain open. in height, are weak and remain upright for In addition to its other attractions, the fra- only a short time before bending over. When grant water-lily has a long blooming season, the apex of the stem touches the surface of from June through September. This species the water, swelling occurs, and aerenchyma is native to southern Canada, the United (spongy with large air spaces) devel- States, Central America, and South America ops, producing adventitious roots that an- and is common in all three ponds at the Ar- chor it. Thus, a new offshoot is established boretum. some distance from the mother plant. This attached floating-leaved hydrophytic This rooted, emergent hydrophytic herb, plant has a thick, fleshy that is or short-lived shrub, has four- to six-sided submerged in the mud and may be long- or stems. The of the submerged parts is short-lived and creeping or branching. The spongy and thick. The leaves are short- floating, rounded leaves are up to 10 inches stalked, opposite or whorled, slender, and wide and are attached by long rubberlike pointed at the tip. The upper leaves have petioles that vary in length according to the clusters of 1 to 3 flowers in their axils. Like water depth. The blades are green and glossy other members of the loosestrife family, the above and purplish on the underside. The 22 .

Swamp Loosestrife (Decodon vertlcillatus/ 23

Fragrant Water-Lily () 24

solitary, sweet-smelling flowers, up to 6 variable in form. The lower, submerged inches wide, have 4 sepals followed by nu- leaves are sessile, alternate, and deeply di- merous spirally arranged petals passing vided into many threadlike segments, while gradually into stamens. The stamens can the floating, glossy leaves, with inflated number from 36 to 100 and the pistils up to petioles and toothed, diamond-shaped 20. When the petals have withered, the blades, form a rosette at the end of each flower stalk forms a spiral shape underwater branch. The inconspicuous, solitary flowers and develops a green fleshy fruit in or near are short stalked in the axils of the leaves the substrate. The seeds emerge when the and consist of 4 green sepals and 4 white fruit decays and spread by floating. This petals. They bloom from July to late August. species can form dense stands rapidly. The fruit is brownish and nutlike.

Water-Chestnut: Trapa natans Pepperwort: quadrifolia Water-Chestnut Family: Trapaceae Pepperwort Family: Marsileaceae

The water-chestnut (Trapa natans) has also A small group of came into existence been known as because of the during the great rise of the flowering plants sharp points on its fruit. A caltrop was a at the end of the period, 300 mil- small bronze or iron ball with projecting lion years after the genesis of other major spikes that Roman soldiers in battle placed fern groups. These ferns adapted to a watery in the path of their foe to incapacitate the environment, and growth in water is still horses. Although the wounds from a water- necessary for the completion of certain chestnut are not incapacitating, they are stages in their life cycle. Pepperwort, or painful. water-clover (), is a This rooted, floating-leaved member of this unusual group. The genus is native to Europe. Introduced into the Marsilea contains about 65 species growing United States in 1884, it has become locally throughout the warmer regions of the world. abundant in the eastern part of the country, Marsilea quadrifolia was first introduced so much so that it is now a nuisance, form- from Europe into this country via Bantan ing impenetrable mats that spread rapidly Lake in Connecticut in 1862. It has spread and hinder navigation, prevent fishing, and throughout New England and into the mid- overcrowd more desirable plants (e.g., bur- western states and is common at the Ar- reed (Sparganium eurycarpum~. State and boretum. federal laws prohibit the importation and This species is a rooted, floating-leaved transportation of this species. The water- hydrophyte that increases in size with the chestnut used in Chinese cooking in this level of the water. The slender, threadlike country is the edible of the sedge rhizomes creep slightly below the mud and . give rise to a delicate, shamrock-shaped leaf The stem of the water-chestnut plant is that may float on the water surface or stand rooted in the mud and has slender leaves erect above the water. 25

Water-Chestnut /Trapa natans) 26

Pepperwort (Marsilea quadmfolia) 27

Unlike most ferns, which generally pro- trates turn the naturally acidic waters of duce their in clusters on the under- eastern Massachusetts nearly neutral, a side of the leaf or , the water-clover condition that is favorable to duckweed. houses its spores in 1 or 2 hard, brown - The genus Lemna is found throughout the shaped structures known as sporocarps. world. Lemna minor is common in drainage These sporocarps are produced on a slender ditches and in the meadow at the Ar- brownish stalk that rises near the base of the boretum. leaf stalk. Each has many com- This plant is a free-floating aquatic herb partments, each containing numerous consisting of a single body called a frond or spores. When the spores are mature, the cap- thallus. This small, flat oval, rarely over’/a sule bursts open vertically into halves, ex- inch long, is not differentiated into leaves or posing the compartments, which are linked stem. It is often purplish beneath with a by a gelatinous ring. This ring floats on the single root attached to each segment. The water with the masses attached. thallus reproduces asexually by buds form- ing groups of two or more plant bodies that often remain attached. The inflorescence is naked or enclosed in a membranous spathe; it is comprised of one pistillate flower, con- Duckweed: Lemna minor sisting solely of one pistil, and two stami- Lemnaceae Duckweed Family: nate flowers, each consisting solely of one The green mantle of the stagnant pool stamen.

- William Shakespeare King Lear Despite its unpleasant appearance, In 1936 a strange phenomenon occurred in duckweed may have significant potential as the Sudbury and Charles Rivers in Massa- a crop plant in the tropics and the sub- chusetts. "Millions of Small Plants Cover tropics, where its growth is profuse. Analy- Charles" one newspaper headline read. ses show that its nutritive value in both "Millions of tiny plants, resembling sham- human and animal diets exceeds that of rocks in color and appearance turned the sur- most agricultural plants; it is high in protein face of the 5 miles of the Auburndale section and amino acids. Wolffia, a genus in the of the Charles River bright green yesterday,"" same family, contains a species that is eaten the article reported. It was soon discovered in northern Thailand. The Thais call it "eggs that the same condition existed in the Sud- of the water." bury, yet the two rivers had no connection whatever. The green phenomenon proved to be an explosion of the duckweed plant /Lemna Common Bladderwort: Utricularia minor), one of the world’s smallest flowering vulgaris and its causes have never been plants, fully Bladderwort Family: Lentibulariaceae understood. It is believed today that a corre- lation exists between the spread of duck- Common bladderwort (Utricularia vulgaris) weed and the presence in the water of is among the comparatively few species of soluble nitrates from sewage. Soluble ni- carnivorous plants. Each tiny bladder on the 28

Duckweed (Lemna mmor/ 29

underwater stem has an opening that func- Skunk Cabbage: Symplocarpus foetidus tions as a trap door. The "door" is pressure Arum Family: Araceae sensitive and when touched opens in 11250th of a second. When the prey enters, the door Skunk cabbage (Symplocarpus foetidus) is it within. Even when it is closes, trapping one of the plants in the Araceae family that too to be contained inside the large bladder, produce enough heat to render themselves the is often held at the and prey opening warmer than the surrounding air. An unusu- the over time. The smal- ingested by plant ally high rate of respiration in these plants is lest traps can catch microscopic single- responsible for the heat, which in the skunk celled and while protozoans rotifers, larger cabbage is retained by the spongy tissue of can catch fish water and traps fry, fleas, the spathe. During the early stages of bloom- larvae. Small such mosquito aquatic plants, ing, the clublike central spadix maintains a as duckweed watermeal (Lemna) and temperature of 36°F to 63°F higher than the have been found in the blad- (Wol f fia also surrounding air (Knutson 1979) for as long as ders. two weeks. This period coincides with the Common bladderwort is distributed maturation of pollen and egg cells, and the the eastern and midwestern throughout heat helps to attract such pollinators as bees. United States and north to southern Lab- Although honeybees do not fly well if air rador and . it is common in Although temperature is below 65°F, they are known New it was found at the Arboretum England, to visit skunk cabbage at temperatures as for the first time last in only year, growing low as 42°F (Knutson 1979). The sweetish shallow water in the smallest pond. scent of the uninjured spathe may also at- This free, submerged hydrophytic plant tract bees. The offensive odor of the spathe lacks roots and grows freely and unattached when damaged is believed to attract insect in the water, usually just beneath the sur- pollinators. face. The plant overwinters by forming The genus Symplocarpus has two widely small clusters of crowded modified leaves disjunct areas of distribution: one in eastern called turions. In cold regions, where the North America, ranging from Quebec and plant must lie dormant for several months Nova Scotia south through New England to and produce winter buds, it usually bears Georgia and Tennessee and west to Min- fewer flowers or none at all and produces nesota and Iowa; the other is in eastern Asia. fruit infrequently. The much dissected seg- Individual skunk cabbage plants are ments produce numerous bladders, and at known to endure for a very long time, possi- the height of the summer as many as 100 can bly even longer than the giant redwoods be seen on a single segment. (Knutson 1979). The species is also present The erect scape arising above the water in and on the eastern edge of the Asian supports as many as 20 yellow flowers that continent. It grows in swamps, muddy resemble small snapdragons. The broad, ground, wet meadows, woods, and along somewhat lobed lower lip is delicately stream banks, often in dense stands. It is not striped in brown and orange and is shorter common at the Arboretum, but it can be than the curved spur. The seeds are brown found in moist, low-lying areas in the and lustrous. See page 2 for illustration. meadow along with cat-tails and irises. 30

Skunk Cabbage (Symplocarpus foetidus) 31

This perennial herb produces many large, some areas, particularly in the Great Lakes clustered basal leaves, which appear as the Region, the St. Lawrence River Valley, and spathe matures. These leaves, which may be the Hudson River Valley. South of the Wis- up to 4 feet in length, are ovate and con- consin glacial border, however, it is scat- spicuously veined. The flower buds develop tered. on the underground rootstocks. By winter, The first report of Lythrum salicaria in shoots several inches in length emerge, with North America was in Pursh’s Flora Amer- one flower bud per shoot forming as lateral icae Septentrionalis in 1814. Two eminent offshoots of the leaf bud. Occasionally, the botanists, John Torrey and Asa Gray, were flower buds are lacking and the leafy shoot doubtful of the previous records, and Gray appears alone. The inflorescence, which is wrote in 1856 that its status as a native plant unique to the arum family, consists of the was "not clear." It was not until 1890, when cream-colored spadix subtended by the the sixth edition of Gray’s Manual of Botany fleshy green-purple or brown-spotted spathe. was published, that the species was treated Many individual flowers cover the spadix, as a plant naturalized from Europe and there- each comprising 4 perianth segments and 4 fore a nonindigenous member of the North fleshy stamens opposite the segments. The American flora. seeds are embedded in the enlarged, spongy The first record of the plant in Massachu- spadix. setts dates from 1844 in Cambridge. By 1900, purple loosestrife was recorded in sev- eral localities throughout the state, and it is believed to have been introduced in the Mer- rimac River Valley through seed washed out Loosestrife: salicaria Purple Lythrum of wool at a plant near Abbots Mill at Loosestrife Family: Lythraceae Graniteville. The stem of this perennial grows to 5 feet, Purple loosestrife (Lythrum salicaria), one of produces narrow, sessile leaves that are op- the more recent additions to the list of nui- posite to whorled and heart shaped at the sance plants, is native to the eastern hemi- base. The purplish red flowers are borne in a sphere, Eurasia, North Africa, and Aus- colorful spikelike panicle, up to 1 foot long, tralia. Palmer, in The Spontaneous Flora of and bloom from June to late August. The the Arnold Arboretum 1930/, described the perianth lobes vary in number from 4 to 6 plant as "common in low meadows and with stamens either equal to or twice the about ponds and sometimes in drier waste number of the petals. ground." Today it forms massive, spectacu- lar colonies in the meadow, around pond margins, and along Bussey Brook and is eliminating some of the native wetland species. Records show that by the late 19th and early 20th centuries this species had spread into the glaciated wetlands of North Amer- ica and had become an aggressive weed in 32

Purple Loosestrife (Lythrum sahcama) 33

Drooping Sedge: Carex crinita The seeds are brownish and somewhat Sedge Family: triangular in shape.

Although the hairy-looking spike drooping from the top of the stem of the sedge is not usually recognized as such, it is in fact a cluster of flowers, and the sedges belong to a Turk’s-cap Lily: Lilium superbum family, the Cyperaceae. Lily Family: Liliaceae Sedges are further designated as monocots, because they produce a single seed-leaf upon Superbum, which means magnificent in . Other monocots include irises, Latin, is an appropriate name for the turk’s lilies, orchids, and rushes. cap, the tallest and most spectacular of our The drooping sedge (Carex crinita) is dis- native lilies. This species also has more tributed throughout the eastern and south- flowers than any other native lily. The eastern United States and is the most com- flower droops gracefully from the tip of the mon wetland species at the Arboretum. It petioles, revealing deep reddish orange pet- grows in large clumps in the meadow and als and sepals splashed with many shades of along pond margins and Bussey Brook. purple and rust-colored anthers. The stems Members of the sedge family are often mis- sometimes reach 9 feet tall. taken for grasses (Gramineae). General differ- Lilium contains about 70 species widely dis- ences between the two families are as follows: tributed throughout the world, with their the sedges have solid stems, closed sheaths, greatest concentration in warm temperate and and 3-ranked leaves, and the fruit has a seed subtropical regions. The turk’s-cap grows in that is not fused to the wall. The grasses wet meadows and low grounds from New have hollow stems, open sheaths, 2-ranked Brunswick to and south to Florida, leaves, and the fruit has a seed joined to the Tennessee, and Missouri and tends to exhibit ovary wall. a more colorful display in moist soil. It is The drooping sedge is a tufted, grasslike common in the meadow at the Arboretum and perennial herb with branching, scaly blooms from June until August. rhizomes. The leaves arise from the base and This perennial herb has a stout, erect stem are long and slender. In the Carex inflores- up to 9 feet tall. The principal leaves are ar- cence the male flowers are borne separately ranged in whorls up to the inflorescence. from the female flowers. The terminal spike The smooth, narrow blades are parallel is staminate, while the subterminal spikes veined and taper at the ends. The spectacular are pistillate, and all these are produced on red-orange flowers are produced in an umbel long, drooping stalks that become progres- or terminal , with as many as 25 sively longer from top to bottom. The female flowers nodding from long pedicels. The flowers are enclosed in a saclike structure perianth segments are strongly recurved, called the perigynium. The stigmas protrude with the curvature beginning below the through the opening at the top of the peri- middle of the segment. Newly opened flow- gynium, and as many as 130 perigynia may ers may not show much curvature, but they comprise one flower spike in this species. do so eventually, exposing the pale green 34

Drooping Sedge (Carex cnmta) 35

Turk’s-Cap Lily (Lilium superbum) 36 ."

Yellow Loosestrife (Lysimachia terrestns) 37

base and deep purple spots. The anthers are streaks above and somewhat whitish be- linear and the is 3-lobed. The fruit is neath. The inflorescence is a raceme, termi- a capsule that splits along 3 lines when ma- nal on the main stem or sometimes in the ture. axils of the branches. The star-shaped flow- Many plants known as lilies do not belong ers, each with 5 basally united yellow petals to the genus Lilium and therefore are not and single maroon eye, are borne on thread- true lilies. Lily of the valley belongs to Con- like pedicels. The filaments are united at the vallaria, day-lily to Hemerocallis, corn-lily base, and the anthers are lavender-purple. to Clintonia, and trout-lily, better known as The seeds are somewhat rounded with a dog-tooth violet, to Erythronium. shiny black surface.

Yellow Loosestrife: Lysimachia Soft Rush: juncus effusus terrestris Rush Family: Primrose Family: Primulaceae Juncus is the largest genus in the family Jun- The yellow loosestrife, or swamp candle caceae and includes about 225 species, most (Lysimachia terrestris), often reproduces of which occur in wetland habitats. About vegetatively by bulbels produced in such 90 species are found within the United areas on the plant as the leaf axis or the States and Canada, and perhaps no species of inflorescence. Linnaeus took these bulbels the genus is more familiar than is juncus ef- to be a parasitic mistletoe species, which he fusus, the soft rush. This plant is widely dis- placed in the mistletoe genus, Viscum. Some tributed in temperate regions of both the populations of this species are quite florifer- northern and southern hemispheres. At the ous and include no bulbel-bearing plants; Arnold Arboretum it is common in the others include bulbel-bearing plants but no meadow and along pond and stream mar- flowers; and still others include plants that gins. exhibit both. This grasslike perennial has vigorous, In North America this plant grows from scaly rhizomes and often forms large, bright Newfoundland and Quebec southward to green tussocks up to 4 feet tall. The soft, South Carolina and westward to Minnesota. basal leaves are quill-like, with chestnut- At the Arboretum it is common in the colored leaf sheaths that are bladeless and meadow and along Bussey Brook, blooming bristle tipped. Associated with the inflores- from late June to August. cence is a stiff involucral bract that is sharp- The rhizomes produce erect, simple or ly pointed and appears to be a continuation branching stems up to 3 feet tall. The leaves of the stem. The inflorescence is an open on the lower stem are scalelike and smaller panicle, consisting of 30 to 100 flowers than the opposite, sessile narrow leaves pro- borne singly on many uneven stalks. The duced further up the stem. The blades are perianth is not differentiated into sepals and punctate with dark purplish dots and short petals but is in two series of three segments 38

Soft Rush ( Juncus effusus) 39

each. The outer whorl is keeled and the white, pink, or purple, is provided by the inner whorl flat. The seed capsule, light cluster of stamens or pistils. (See inside front brown and smooth, is 3-sided and rounded at cover for illustration.) the apices. The seeds are small with darker short-pointed extremities. For more than a century the soft rush has been a wetland crop in Taiwan, , Korea, and Japan, where the dried stems are used for floor matting.

Tall Meadow-Rue: Thalictrum polygamum ’ Buttercup Family: Ranunculaceae Tall meadow-rue (Thalictrum polygamum) is one of the most easily located plants in the field, as its masses of soft, feathery white flowers rise above most other wetland plants. This perennial herb grows to 11 feet tall and can be found in wetlands, swamps, and low thickets from Newfoundland to On- tario, south to Nova Scotia, Georgia, and Tennessee. At the Arboretum it is common in the meadow and along Bussey Brook, blooming from June through September. The stems of tall meadow-rue are light green at first but become tinged with magenta later in the season. The leaves are pinnate, with 3 or more leaflets. The large, graceful, terminal panicles can be rounded or flat at the top. Some plants display pure white flowers while others produce purplish flowers. Meadow-rue includes perfect (con- taining both stamens and pistils) and uni- sexual (containing only stamens or only pistils) flowers on single plants. Botanists have termed this conditionpolygamous, and the species name polygamum refers to this. The achenes (small, dry, one-seeded fruits) are short-stalked. This species has no pet- als, so the color of the flower, which can be 40

A Species List of Aquatic and Wet- Eleocharis ovata /Roth~ R. 8, S p Eleochans palustns (L.) R. & S. p m land Plants Observed in the Rynchospora capitellata (Mtchx.) Vahl - beak rush Arboretum Since 1930 pm Scirpus atrocmctus Fern. m Monocotyledons (Monocotyledoneae) Scmpus atromrens Willd. - dusky bulrush m s Scirpus cypennus (L.) Kunth-wool-grass m s Plants with all or some of the following characters: vas- Scirpus expansus Fern. p m s cular bundles distinct and scattered in the intemodes ; Scirpus polyphyllus Vahl m or seed flowers with usu- cotyledon, leaf, solitary, parts Gramineae - Grass Family ally m 3s or multiples of 3; leaves parallel-veined; Alopecurus gemculatus L. m fibrous root herbaceous. system; usually - plants Alopecurus pratensi L. meadow-foxtarl m s Alismataceae - Water-Plantain Family Anthoxanthum odoratum L - sweet vernal grass m Ahsma subcordatum Raf. - water-plantain p m s Calamagrosus canadensis (M~chx.l Nutt.-blue-~omt Ahsma trmale Pursh-water-plantam p m s grass p m s Sagittaria latifolia Willd. - duck-potato p m s Cmna arundmacea L. -wood reedgrass p m s Dactyhs glomerata L. - orchard grass m Araceae - Arum Family Glycena acutiflora Torr. p Acorus calamus L. - s sweetflag p Glycena canadensis (Michx.) Trm. 2014 rattlesnake- Peltandra mrgm~ca (L.~ Schott & Endl. - arrow-arum p grass s foetidus Nutt. - skunk m /L.) cabbage -- Symplocarpus Glyceria grandis S. Wats. reed-meadow grass p m Callitrichaceae - Water-Starwort Family Glycena laxa Scnbn - northern manna-grass p m Calhtmche heterophvlla Pursh - water-starwort p s Glycena palhda (Torr I Tnn.-pale manna-grass p Glvceria stnata /Lam ~ Hitchc. - fowl-meadow grass Cyperaceae - Sedge Family pmss Carex annectens Bickn. - fox s yellow sedge p - Leersia oryzoides (L.~ Sw. nce-cutgrass p ms Carex blanda Dew. m Leersia mrgmica Willd - whitegrass p s Carex canescens L. m s Muhlenbergia schreben J. F Gmel-drop-seed grass m Carex conoidea m Schkuhr-silvery sedge Phalams arundmacea L. - reed-canary grass m s Carex cnmta Lam. - m s drooping sedge Phleum pratense L - timothy m Carex debihs Michx. m s p - Poa compressa L. Canada bluegrass m Carex echmata Murr. m Poa palustris L. m s Carex hirta L. m Poa pratensis L. - Kentucky bluegrass m Carex hystricma Muhl. - porcupine sedge m s Sparuna pecunata Lmk- cord-grass s Carexlanugmosa Michx. m Carex lupulma Muhl. p Indaceae - Iris Family

- Carex lunda Wahlenb. - sallow sedge m Ins pseudacorus L. yellow ms p m s Carex pallescens L.-pale sedge m s Ins versicolor L. - common blue flag p m s Carex pamcea L. m Sisynnchmm atlanucum Bickn. m Carex Schkukr m scopana Juncaceae- Rush Family Carex stncta Lam. - tussock sedge m juncus bufomus L - toad-rush m Carex stipata Muhl. - awl-fruited sedge m juncus canadensis J. Gay m Carex tnbuloides Wahlenb. p m s juncus d~chotomus Ell. m Carex vulpmoidea Michx. m juncus effusus L. p m s Cyperus stngosus L. - straw-colored sedge p m juncus margmatus Rostk. m Eleochans aciculans R. & S.-least m /L.) spike-rush - juncus tenms Willd. tufted rush m Eleocharis calva Torr. p Eleochans gemculata (L.) R. & S. p Lemnaceae - Duckweed Family

- Eleochans obtusa (Willd.) Schultes - blunt spike-rush Lemna minor L. duckweed p s pmss Liliaceae - Lily Family Lihum canadense L. - Canada lily m p pond Lihum philadelphicum L.-wood-hly m m meadow Lilium superbum L. - turk’s-cap lily m s stream Uvulama sessihfoha L.-mld-oats s 41

Orchidaceae - Orchid Family Eupatonum dubmm Willd. - Joe-pye-weed p Habenana lacera (Michx.) Lodd. - ragged orchis m Eupatonum perfohatum L.-thoroughwort m Habenana psycodes ~L.~ Spreng. - purple-fringed Sohdago canadensis L. - Canadian goldenrod m s orchis s Tanacetum vulgare L. - tansy p m s Spmanthes cernua (L.) Richard -nodding ladies-tresses ms s Convolvulaceae - Convolvulus Family Spiranthes gracihs (Bigel.) Beck - southern slender Convolvulus sepmm L.-hedge bmdweed m ladies-tresses m Cuscuta gronovm Willd. - common dodder m s Spiranthes tuberosa Raf. 2014little ladies-tresses m Cuscuta pentagona Engelm. s - Pondweed Family Cruciferae - Mustard Raf. - pondweed p Family Barbarea R. Br. rocket m s Potamogeton fohosus Raf. - pondweed p vulgans -yellow Diplotaxis murahs /L.) DC. - sand rocket p Spargamaceae - Bur-Reed Family Ronppa nasturtium-aquaticum /L.~ Bntten & Rendl. bur-reed Spargamum eurycarpum Engelm. - p (Nasturium officmale R. Br.) p s Typhaceae - Cat-tail Family Ronppa palustns /L.) - Bess-marsh cress p m

L. - broad-leaved cat-tail s Typha laufolia p m Euphorbiaceae - Spurge Familyy Acalypha mrgmica L. - three-seeded mercury m Gentianaceae - Gentian Family Gentiana cnmta Froel. -fnnged gentian m (Dicotyledoneae) Hypericum boreale /Bntt.) Bickn. p ’ Hypencum canadense L. m Plants with all or some of the following characters: vas- Hypencum mo~us (Gray) Bntt. m cular bundles of stem m a scat- usually ring (sometimes - Hypemcum mutilum L. slender St. John’s-wort p m s tered m a few aquatics); cotyledons usually 2 or rarely 1 m a few aquatics; flowers with parts usually m multi- Labiatae - Mmt Family ples of 2, 5, or more; leaves pmnately or palmately Lycopus amencanus Muhl. - cut-leaved water- vemed; roots usually fibrous; plants herbaceous or horehound p m s woody. Lycopus umflorus Michx. - water-horehound p m s Lycopus vmgmicus L. - water-horehound s Milkweed Asclepladaceae - Family Mentha arvensis L. - field mmt p m s L. - s Asclepias mcarnata swamp-milkweed p - Prunella vulgans L. selfheal m Balsaminaceae 2014 Touch-Me-Not Family Scutellana latenflora L. - mad-dog skullcap m Impatiens capensis Meerb. - spotted touch-me-not Lentibularlaceae - Bladderwort Family pmss Utmculana vulgans L - common bladderwort p Boraginaceae 2014 Borage Family Lobehaceae - Lobelia Family L. - s Myosotis - scorpiordes forget-me-not Lobeho cardmahs L. cardmal flower p

Capnfoliaceae - Honeysuckle Family Lobeha siphihtica L - great blue lobeha m s

Samrucus canadensis m , L - elderberry Lythraceae - Loosestnfe Family

Chenopodiaceae - Goosefoot Family Decodon verticillatus (L./ Ell. - swamp loosestrife p Chenopodmm glaucum L. - oak-leaved goosefoot m Lythrum sahcana L. -purple loosestnfe p m s

Compositae - Composite Family Malvaceae - Mallow Family Asterlaems L -smooth aster m Malva moschata L. musk-mallow p Asterlatemflorus /L.~ Britt. m s Nymphaeaceae - Water-Lily Family Aster L - New aster s novi-belgii England p m Nymphaea odorata Ait. - fragrant water-lily p Asterpumceus L - purple-stemmed aster m s Aster simplex Willd. - tall white aster p Onagraceae - Evemng-Pnmrose Family Aster mmmeus Lam. - small white aster m s Epilobmm coloratum Biehler-purple-stemmed

Bidens cernua L. - stick-tight p m s willow-herb m s connata Muhl - beggar-ticks p m s Ludwigia palustns (L.) Ell. - water-purslane p

- Bidens frondosa L. - beggar-ticks p m s Oenothera bienms L. common evening pnmrose m Bidens vulgata Greene - beggar-ticks p m s Oenothera perenms L. - sundrops p m 42

- Polygonaceae Buckwheat Family Smm suave Walt. - water-parsmp p m s L. p Polygonum omphibmm - water-smartweed - Urticaceae Nettle Family Polygonum anfollum L. - halberd-leaved tearthumb Pilea pumila (L.) Gray - clearweed m pm Polygonum aviculare L. - knotweed m Verbenaceae - Vervain Family Polygonum coccmeum Muhl. - swamp smartweed Verbena hastata L - blue vervain m pmss Violaceae - Violet Family Polygonum hydropiper L. - water-pepper p m s Viola cucullata Ait. - marsh blue violet m Polygonum hydropiperoides Michx. - mild water- Viola lanceolata L. -lance-leaved violet p m s pepper p m Viola pallens (Banks) - brainerd-sweet white violet Polygonum lapathifohum L. p mss Polygonum punctatum Ell. - water-smartweed m Viola Pursh- common blue violet m - papilionacea Polygonum sagittatum L. arrow-leaved tearthumb pm Rumex obtusi fohus L. - bitter dock m (Pteriodophyta) Pontedenaceae - Pickerelweed Family Pontedena cordata L. -pickerelweed p Plants that are fernlike, rushlike, mosslike, or quill- leaved and have no seeds or flowers but reproduce by Pnmulaceae - Pnmrose Family spores. Hottoma mflata Ell. - featherfoll p Lysimachia quadnfoha L. - whorled loosestrife m Eqmsetaceae - Horsetail Family Lysimachia terrestns (L.) BSP. - yellow loosestrife m Eqmsetum arvense L. - field horsetail p Equisetum fluviatile L. - water horsetail p Ranunculaceae - Buttercup Family Eqmsetum sylvaticum L. m Ranunculus acns L.-tall buttercup m

- Ranunculus repens L. - creeping buttercup m s Lycopodiaceae Club Moss Family Thahctrum polygamum Muhl. - tall meadow-rue m s Lycopodium complanatum L. - trailing ground-pine ms s Rosaceae - Rose Family

- Rubus hispidus L. - dewberry m Marsileaceae Pepperwort Family Marsilea quadmfoha L. - pepperwort p Rubiaceae - Madder Family Gahum palustre L. - marsh bedstraw m Osmundaceae - Flowering Fern Family

- Gallum tmctomum L. - marsh bedstraw m Osmunda cinnamomea L. cinnamon-fem s Osmunda claytomana L. - mterrupted fern m s -

Saxifragaceae Saxifrage Family - Osmunda regahs L. royal fem m s Penthorum sedoides L. - ditch-stonecrop m Polypodiaceae - Fern Family

Scrophulanaceae - Figwort Family Onoclea sensibihs L. - sensitive fern s Agahms paupercula (Gray) Pennell- small gerardia p m Dryoptens thelyptens (L.) Gray - marsh shield fem m ms s Agahms tenmfoha /Vahl.) Raf.-slendergerardia m s Chelone glabra L. - turtlehead p m s Lmderma dubia /L.~ Pennell - false pimpernel p m Mimulus nngens L. - monkey-flower m s

Veromca of~cmahs L.-common speedwell m I Veromca scutellata L. - marsh speedwell p Solanaceae- Nightshade Family Solanum dulcamara L. - bittersweet nightshade s Trapaceae - Water-Chestnut Family Trapa natans L. - water-chestnut p

Umbelhferae - Parsley Family - bulbifera L. - water hemlock p s Cicuta maculata L. - spotted cowbane p m s Hydrocotyle amencana L. - water pennywort m 43

References southeastern United States. Journal of the Ar- nold Arboretum 45: 235-250. Adams, P., and R. K. Godfrey. 1961. Observations cf the Gupta, K. M. 1957. Some species of Marsilea with spe- Sagittana subulata complex. Rhodora 63: 247- cial reference to their epidermal and soral charac- 266. ters. Madrono 14: 113-127. Anderson, E. 1928. The problem of species m the north- Hendricks, A. J. 1957. A revision of the genus Alisma em blue-flags Ins versicolor L. Annals of the (Dill.) L. Amencan Midland Naturahst 52: 470- Missouri Botanical Garden 15: 24-332. 493. . 1936.The species problem m Ins. Annals of the Hicks, L. E. 1932. Flower production m the Lemnaceae. Missouri Botamcal Garden 23: 457-509 Ohio Journal of Science 32: 115-131. Blackwell, W. H., Jr., 1972. The combmarionPeltandza Hotchkiss, N., and H. L. Dozier. 1949. and virginica (L.) Schott & Endlicher. Rhodora 74: distribution of North Amencan cat-tails. Amer- 516-518. ican Midland Natuzahst 41: 237-254. Bogm, C. 1955. Revision of the genus Sagittana (Alis- Knutson, R. M. 1979. Plants m heat. Natural History mataceae). Memoirs of the New York Botanical 88/3/: 42-47. Garden 9: 179-233. Koehne, E. 1885. The Lythraceae of the United States. Cody, W. J. 1961. Ins pseudacorus L. escaped from cul- Botanical Gazette 10(5): 269-277. tivation m Canada. The Canadian Field Lawrence, G. N. M. 1951. Taxonomy of Vascular Naturahst 75: 139-142. Plants. Macmillan, New York. Conrad, M. S. 1905. The Water Lihes~ A Monograph of Li, Hui-Lm. 1955. Classification and phylogeny of the Genus Nymphaea. Pubhcation of the Car- Nymphaceae and allied families. American Mid- negie Institution Waslvngton 4: 1-279 land Naturahst 54: 33~1. Cook, C. D. K., B. J. Gut, E. M. Rix, J. Schneller, and Lowden, R. M. 1973. Revision of the genusPontedena. M. Seitz. 1974. Water Plants of the World. Dr. Rhodora 75: 426-487. W. Junk b.v., Pubhshers, The Hague. Mahabale, T. S. 1972. Water fems: Their origin and Crocker, W. 1907. Germination of seeds of water plants. spread. Birbal Sahm, Institute of Palaeobotany Botanical Gazette 44: 375-380. Lucknow, Poona, . Crocker, W., and W. E. Davis. 1914. Delayed germina- Palmer, E. J. 1930. The spontaneous flora of the Arnold tion in seed of Ahsma plantago. Botamcal Arboretum. Journal of the Arnold Arboretum 11: Gazette 58: 285-321. 63-119. R. Lemna mmor as an weed m Eaton, J. 1947. aggressive . 1935. Supplement to the spontaneous flora of the Sudbury Rmer. Rhodora 49~ 165-171. the Arnold Arboretum. Journal of the Arnold Ar- Fassett, N. C. 1957. A Manual of Aquauc Plants. Um- boretum 16: 81-97. versity of Wisconsm Press, Madison, Wisconsm. Ad Hoc Panel of the Advisory Committee on Technol- Fassett, N. C., and B. Calhoun. 1952. Introgression be- ogy Innovation, Board on Science and Technol- tween Typha lattfoha and Typha angusufoha. ogy for International Development, Commission Evolution 6: 367-379. on International Relations. 1976. Making Aquat- Fernald, M. L. 1970. Gray’s Manual of Botany, 8th edi- ic Weeds Useful.~ Some Perspectmes for Devel- tion. D. Van Nostrand Company, New York. oping Countries. National Academy of Sciences, Fernald, M. L., and K. M Wiegand. 1910. The North , D.C. Amencan variations of {uncus effusus. Rhodora Rossbach, G. B. 1939. Aquatic Utmculanas. Rhodora 12: 81-93. 41: 113-128. . 1905. The hybnd of Lysimachia terrestns and Saeger, A. 1929. The flowering of Lemnaceae. Bulletm Lysimachia thyzsiflora. Rhodora 52: 199-201. of the Torrey Botanical Club. 56: 351-358. H. A. Brown Illus- Gleason, 1952. The New Bntton and Schrenk, J. 1889. On the floating tissue of Nesaea ver- trated Flora of the Umted States and Ad~acent ticillata (L.) MBK. Bulleun of the TorreyBotam- Canada Lancaster Press, Lancaster, Pennsyl- cal Club 16: 315-23. vania. Skitch, A. F. 1928. The capture of prey by the bladder- Godfrey, R. K., and J. W. Wooten. 1979. Aquatic and wort : a review of the physiology of bladders. New Wetland Plants of the Southeastern Umted Phytologist 27’ 261-97. States. The University of Georgia Press, Athens, Slack, A. 1980. Cazmvozous Plants. Massachusetts In- Georgia. stitute of Technology Press, Cambndge, Massa- Graham, S. A. 1964. The genera of Lythraceae in the chusetts. 44

Small, J. K. 1931. The water lilies of the Umted States. Journal of the New York Botamc Garden 32: 117-121. Smith, S. G. 1967. Experimental and Natural Hybrids m North Amencan Typha (Typhaceae). American Midland Naturalist 78: 257-87. Stason, M. 1926. The Marsileas of the western Umted States. Bulletm of the Torrey Botamcal Club 53: 473-78. Stuckey, R. L. 1980. Distributional history of Lythrum sahcana (purple loosestrife) in North America. Bartoma 47: 3-20. Tomlinson, P. B. 1982. Helobiae /Alismatidae~. Vol. 7 in Anatomy of the Monocotyledons, C. R. Metcalfe, ed. Clarendon Press, Oxford. West, D., and D. F. Whigham. 1976. Seed germination of arrow-arum (Peltandra vmgmica L.). Bartoma 44: 44-49. Wood, C. E. 1959. The genera of the Nymphaeaceae and m the southeastern Umted States. Journal of the Arnold Arboretum 40~ 94- 112. Wooten, J. W. 1973. Taxonomy of seven species of Sagittana from eastern North Amenca. Bartoma 25: 64-74.

~

Patncia A. Dalton is the author of Wildflowers of the Northeast m the Audubon Fairchild Garden (Audubon Center in GreenmchJ. She has been updatmg the rec- ords of the Immg collections at the Arnold Arboretum during the past two years.

Ale~andro Novelo R. is a taxonomist speciahzmg m aquatic plants at the Umversidad Nacional Autonoma , de Mexico in Mexico City. Amy Storey is an artist and botamcalillustratorlmng in , Bmush Columbia.