8o YEARBOOK OF AGRICULTURE 1961 may resist germination for long periods. Some species produce pods in which one segment remains indéhiscent— closed—and the seed within it remains Plants Must Disperse dormant for a long time, as in cockle- bur (Xanthium), for example.

Their Seeds THE DISPERSAL of seeds is determined largely by the size, shape, and char- acter of the seedcoat or the persisting PAUL G. RUSSELL AND ALBINA F. MUSIL structures of the fruit as, for example, the awns of grasses; the ''fuzz" of cot- ton; spines and bristles of various NOT ALL SEEDS survive the struggle for forms; "wings" on the seeds of certain existence. Any marked change in trees; plumes of dandelion and thistle; environment, moisture, temperature, the forceful opening of the seed pod, amount of sunlight, or soil composition as in witch-hazel {Hamamelis virginica) ; may create conditions under which and a sticky surface when wet. seeds of certain plants cannot germi- Such seeds are dispersed readily by nate. Plants therefore must disperse such, natural means as wind, water, their seeds in such a manner and animals, and birds. in such quantity that some, at least, When structures, such as awns and will survive so that the species may pubescence, have been removed in the continue. process of harvesting and cleaning of Devices for survival among plants crop seeds, such seeds may become are many. widely distributed in any of several The dormant embryonic plant with- ways—with crop seeds, feeds (hay and in the seed of most kinds of plants is grain), common carriers (trucks, auto- protected by a seedcoat until condi- mobiles, wagons, airplanes), farm im- tions are favorable for new grow^th to plements, ships, birds, and insects. start. The seedcoat may be tough, as The natural means of dispersal have in the bean. It may be thin and been lost long since by most of our delicate, as in the peanut, in which it cultivated seed crops, like the cereals, is protected by the shell of the fruit. beans, and peanuts. Many persons are The struggle for existence is re- not aware of that fact. Only the con- flected also in the amazing variety of stant, watchful efí'orts of man enable shapes, structures, and sizes of seeds these seed crops to withstand the effects and fruits among the 300 families of of unfavorable wxather and the on- flowering plants. slaughts of insect pests and diseases A variable proportion of seeds of and continue their roles as valuable many kinds of plants resists prompt sources of food. germination and so assures survival if Another fact is that the quality and conditions are unfavorable for some quantity of production would begin to of the seeds that germinate first. One deteriorate very soon were it not for example is the uneven ripening and the continuous research of the plant shedding of the fruits of some grasses, breeders and geneticists. Through the such as giant foxtail {Setaria faberi). selection and hybridization of plants, Another is the delayed shedding of the they are constantly developing new seeds (achenes) produced from the ray strains and varieties of all the main flowers of certain composites, such as seed crops. The improved species are some species of thistles. increasingly superior to the original Many legumes, such as the clovers, wild types to which all would revert if produce a variable proportion of seeds left to the uncertain natural means of with impermeable seedcoats, which spreading. PLANTS MUST DISPERSE THEIR SEEDS 8i

WIND DISPERSAL is the commonest carried by the wind to great distances. means of dispersal. Strong winds dur- Sometimes they float in the air for ing storms may carry rather heavy long periods. Seeds of some orchids are equipped with thin, tiny wings, which add to their buoyancy. Tumbleweeds when they are dry and ripe may be torn loose by the wind and blown over the ground. Seeds drop along the way. Tumbleweeds are known on deserts, prairies, and steppes throughout the world. An example is an amaranth {Amar- anfhus graecizans)^ a weed that is com- monly found here and there in drier areas throughout the United States, especially in the western plains. The tumbleweed is so characteristic of our West that the name figures promi- nently in songs. Another example is the noxious Russian-thistle (Salsola pestifer), w^hich is not a true thistle but is closely related to the pigweeds. The wind blows the plants in every direc- The witchweed has very liny seeds, only ^ mm. tion, especially in winter when the long, and one plant produces jo thousand to joo ground is frozen, and the small, conical thousand seeds. It is a dangerous parasitic weed (Striga asiática), and attacks corn, sorghum, seeds arc scattered in all directions. sugarcane, and other grasses. Plants of the mustard family, such as the shepherds-purse {Capsella bursa- pastor is), an annual weed, have pods seeds and seedUke fruits, regardless of in which the seeds remain. The seeds structure, for miles. Even a light breeze are attached to a partition between the may transport small, light seeds for two halves of the pod. The partition some distance. and the seeds are blown aw^ay by the Dispersal by wind often is facilitated wind and are distributed widely. One by the small size of certain seeds. large plant may bear 500 seed pods, Possibly the smallest known are those each with about 24 seeds. of the witchweed {Striga asiática)., an In the fieldcress (Lepidium campestre), Asiatic parasitic plant that has been wild peppcrgrass (L. virginicum), and found in two Southern States. The tiny other species of Lepidium, the small, seeds, only 0.0078 inch long, arc pro- round, flat, papery half pods, each duced in enormous quantities—50 with one flattened seed, are blown thousand to 500 thousand on one about by the wind for considerable plant. Because of their minute size, distances. they are easily dispersed by water, Many plants have wdnged seeds or wind, and farm implements. The winged, seedlike fruits by which their witchweed has long been known in distribution is facilitated through wind Old World Tropics and subtropics. It dispersal. They are more likely to is a dangerous parasite that attacks occur on trees, tall shrubs, and high, corn, sorghum, sugarcane, and other woody vines than on low, herbaceous grasses. plants. The orchid family (Orchidaceae) The winged keys of the maples are also has extremely small seeds. Some familiar to everyone. So are the genera have seeds so fine they resemble winged nutlets of the ashes (Fraxinus). dust. Freed from the capsule, they are Many trees of the pine family have 050888°—Gl 7 82 YEARBOOK OF AGRICULTURE 1961 winged seeds that are samaroid—that Many herbaceous plants also have is, they resemble the small, dry, seeds and seedlike fruits that are dis- winged, seedlike fruits of the maple persed by wind with the aid of various and elms. Most of the pines (Pinus) have seeds of this type, as do the spruces {Picea)^ the firs {Abies)^ the cypresses {Cupressus), the tamaracks {Larix), and the true cedars {Cedrus). 5=^,^^. The elms {Ulmus) and the crapemyrtle {Lagersiroemia indica) also have small, samaroid seeds. The handsome tree-of-heaven {Ail- anthus altissima), popular as a street The airplane seed, borne by an East Lidian cucurbit vine (Macrozanonia macrocarpa), is tree because of its adaptability to city about 6 inches wide, and derives its common name conditions, has large clusters of sama- from the fact that it describes a spiral about 20 feet ras. The seed is in the center of the wide as it falls to the ground from the urn-shaped long, narrow wing. The sweetgum capsule. {Liquidambar styraciflua) has samaroid seeds about one-fourth inch long that are blown about freely by the wind in types of wing. One is an East Indian cu- autumn. curbit vine {Macrozanonia macrocarpa), The seeds in the samaroid group that which has a flat seed an inch across. have only one terminal wing rotate A wing about 3 inches long and 2 briskly in the wind as they travel, and inches wide is on each end. It has been the area of their distribution thus is called the airplane seed, because it greatly extended. describes a spiral about 20 feet wide True yams {Dioscorea), of which when it falls to the ground from its there are more than 600 tropical and urn-shaped capsule on the high-climb- subtropical species, arc climbers with ing vine. winged seeds. The wings are attached The true lilies {Lilium), popular as to the seeds in various ways, but in ornamentals throughout the Temper- most species the thin, papery seeds are ate Zones, have thin, flat seeds, dis- winged on both sides. tinctly winged all around. From the The small, light, flat seeds of many many-seeded capsules, often borne at of the rhododendrons are winged, the summit of the stalk, the seeds are usually all around, and fly readily in blown away a few at a time, especially the wind. The leathery, ovoid capsules after the stalk becomes withered. of the handsome paulownia {Paulownia On the plains of South. Africa, a tomentosa) enclose great numbers of similar method of dispersal may be small, delicate seeds, each of which has observed in certain of the native several wings. gladiolus {Gladiolus), We get quinine from South Ameri- Some of the rockcresses (Arabis) have can trees {Cinchona). Their small, ob- long, narrow pods that release to the long, samaroid seeds are one-fourth to breeze small, elliptic seeds that have one-half inch long and have irregular, marginal wings. These low, herbaceous terminal wings. They are so light that alpines, of the mustard family, have they are easily carried for considerable terminal clusters of attractive pink, distances by even gentle breezes. white, or purple flowers. The horseradish-tree {Moringa olei- The ovoid capsules of an attractive fera), grown throughout India, has native white-flowered perennial, the curious, wind-dispersed, three-angled, turdehead {Chelone glabra) enclose winged seeds, which yield a valuable numerous small, flat, squarish seeds, oil. The seeds are discharged from a which are surrounded by a broad, large ribbed pod 9 to 18 inches long. membranous wing, well suited for wind PLANTS MUST DISPERSE THEIR SEEDS 83 dispersal when it is released from the erally fly much farther than winged upper part of the plant. ones. Some travel hundreds of miles. The large carrot family has two They usually are very light. They can principal means of seed dispersal. Each rise and fall with the wind and even fruit consists of a pair of round or rise again from the ground. Most of oblong carpels, which are attached to them are weeds. a slender axis, or columella. Each The common dandelion {Taraxacum contains one seed, is usually indéhis- officinale) has plumed achenes, which cent, and often is furnished on the float gracefully in the breeze. Closely outer side with several ribs that are related genera in the chicory family sometimes elevated into wings. These that have similar structures are the fruits usually are borne on a tall stalk, sowthistles {Sonchus), wild lettuces which in some species is several feet {Lactuca)^ salsify {Tragopogón)^ and high. When the whole plant becomes several others. dry and brittle, the light, corky fruits Among the grasses, the spike pappus- are easily dislodged by the wind and grass {Enneapogon desvauxii) has plu- carried away. The wings enhance the mose awns, which enable the wind to buoyancy. carry ofl" the mature florets. Fruits of the wild carrot have de- In the aster family are a great many veloped bristles, with or without hooks, genera with seeds (achenes) that have that enable the fruits to adhere to the bristles or hairs light enough to permit fur of passing animals. Thus they get the wind to broadcast them. Some are distributed. pernicious weeds. The Canada thistle Among the most serious pests of {Cirsium arvense) is one of the worst western ranges, the halogeton {Halo- weeds in various parts of the North gefon glomeratus) is especially danger- Temperate Zone because the plumed ous, because it is poisonous to live- seeds are easily carried aloft. The stock. Its small, seedlike, winged fruits knapweeds {Centaurea)^ ironweeds {Ver- are dispersed easily by wind. nonia), and the érigerons {Erigeron) are The Russian-thistle {Salsola pestifer) ^ other troublesome weeds that are another noxious weed, also has small similar to the common thistle in their winged seeds. adaptations for dispersal by wind. A number of plants have seeds that Most of the milkweed family (As- are not actually winged but are flat clepiadaceae), many genera of the dog- and membranous, borne in capsules, bane family (Apocynaceae), and some and easily carried by wind. One ex- genera of the evening-primrose family, ample is the tulip {Tulipa). Its light, such as the fireweed {Epilobium angustí- flattened seeds occasionally have nar- folium) y have comose seeds—^that is, row marginal wings. Another is the with a tuft of hairs attached to one end. yucca {Tueca)^ native mostly to the An example from the dogbane family more arid regions of our country. Its is the Strophanthus from tropical Africa large, flat, black, wind borne seeds are and tropical Asia. The apex of the seed produced in great abundance. is prolonged into a long, slender beak The wind disperses the "seeds" of that is densely feathered along the many grasses, although generally there upper half with thin, white hairs. is no special structural adaptation for From the seeds of certain species of this purpose except the lightness of the Strophanthus^ sarmentogenin is derived; chafly lemmas and paleas that enclose it contributed to the synthesis of corti- the grain and act as a wing. Many also sone, a drug used in the treatment of have silky hairs on the callus. One is arthritis. the common, reed {Phragmites commu- In the common milkweed {Asclepias nis), whose long hairs enable the floret syriaca), the large coma, or tuft of hairs, to fly away. helps the wind carry the seed away. Plumed seeds and scedlike fruits gen- Almost any type of seed can be 84 YEARBOOK OF AGRICULTURE 1961 transported by some kind of water these and other conditions. They rep- movement—rainwash, floods, and the resent relatively few species, compared action of streams. Very small seeds, with those dispersed by wind and those that are light in proportion to animals. their size, and those with flat shapes Several genera of the bean family that make for greater buoyancy, are appear among those successfully estab- moved greater distances than other lished by this means in widespread kinds. areas in the Tropics. They include Many of the light, corky secdlike Mucuna, Guilandina, Eniada^ Erjthrina, fruits of the carrot family float easily, and Vigna. In most of them, buoyancy some for several months, as do also is maintained by a relatively large seeds of some of the gourd family, cavity between the cotyledons. Seeds which also owe their buoyancy to their cast up on the Florida beaches and light, corky structure. Seeds of both along the gulf coast picked up rather these groups are mostly transported by frequently by tourists nearly always streams. belong to these genera. Some of them The thick-walled, buoyant achenes apparently have come from as far as of the silverweed {Potentilla anserina) eastern South America. have been known to float in streams for 15 months. The weed therefore ANIMALS and birds disperse, seeds, is widespread along riverbanks and in too. We often see them in late summer swampy meadows in the Northern and early autumn with numerous seed- Hemisphere. like fruits adhering to their hides or The jimsonweed {Datura stramonium) feathers—as happens also to the has flat, corky seeds that float easily. clothing of those of us. who walk in the In South Africa, and doubtless else- fields and woods. A large number of where, they are carried downstream loy plants, including many weeds, owe floodwaters and deposited on the river- their distribution to this type of seed banks, where they germinate. dispersal. Hairs, bristles, or hooks on The seedlike achenes of the buck- the surface of their fruits and muci- wheat family (Polygonaceae) are often laginous seedcoats in some instances dispersed by water, as shown by their help them attach themselves to fur, common occurrence along riverbanks. feather, and fabric. In the docks (Rumex) that have winged The bur-ragweed (Franseria tomen- seeds, the wings apparently serve for tosa), a pernicious w^eed in the Western dispersal by both wind and water. States, has burlike achenes that are Certain sedges (Carex), of which armed with several rows of hooked there are about a thousand species, spines, which adhere readily to passing have seeds (achenes) that contain air animals. The barbed bristles of the pockets and float on water, sometimes beggarticks {Bidens) are well adapted for several months before the seed to adhere to animal fur, bird's plum- may find conditions favorable for age, and clothing. The genus is known germination. almost throughout the world. Some seeds and seedlike fruits are The tick-trefoils (Desmodium) are carried by ocean currents. Such seeds equally adhesive. Their small, flat, in- are of the kind that can float for a long dehiscent pods are covered with period without absorbing sea water hooked hairs. and establish themselves finally in tidal The wild carrot (Daucus carota) and mud or on beaches. They must have a some other species of Daucus have hard, waterproof seedcoat and the seeds (mericarps) with hooked bristles. ability to respond to external influ- The same is true of the species of the ences. Of the immense number of seeds weedy snakeroots (Sanicula), floated down into the sea by streams The seedlike nutlets of one stickseed all over the world, only a few fulfill (Lappula echinata) are armed with a PLANTS MUST DISPERSE THEIR SEEDS 85 double row of hooked prickles, which tachment, and the seeds are violently become embedded in sheep's wool in ejected, together with the mucilagi- the Western States and are thus likely nous liquid with which they were sur- to lower the grade of the wool. rounded. The explosion may throw Another troublesome weed, the the seeds as far as 20 feet. Sometimes houndstongue {Cynoglossum officinale)^ these adhere to some passing animal closely related to the stickseed, also has that had set off the explosion by nutlets with short, barbed prickles. touching the ripe fruit. The small mistletoe {Arceuthobiuin THE GLUEY SEEDGOATS of some spe- pusillum) of New England is parasitic cies make it relatively simple for the on the black spruce. When its berries seeds to become widely dispersed. are ripe in September, the seeds are Seeds of the butterfly-pea (Clitoria violently expelled. The mucilaginous mariana), a leguminous plant with matter on the seeds causes them to showy, pale-blue flowxrs, are so viscid stick to other parts of the spruce or that they adhere to any passing ani- to nearby trees, upon which they mal. Several other species of Clitoria germinate. from tropical America and Asia also Another annual vine {Cyclanthera ex- have sticky seeds. plodens) has small, spiny, gourdlike Seeds of another rather large group fruits about 1.5 inches long. They of plants are viscid only after being burst open into three lobes when they wetted. The plantains (Planiago), with are ripe, and the seeds are thrown out. species, mostly weeds, all over the In some species of Oxalis, as O. world, belong in this group, as do also stricta, often a weed in gardens and many of the rushes (Jiincus), some of elsewhere, the small, cylindrical cap- the flaxes {Linum)^ and several of the sule suddenly explodes when touched members of the mustard family, in- and scatters its seeds. cluding the garden cress {Lepidium The pale touch-me-not {Impatiens satirjum), the common falseflax (Came- pallida) and other species of Impatiens Una sativa)^ and the shepherds-purse have narrow capsules that open sud- {Capsella hursa-pastoris), all more or denly to broadcast their seeds. less weedy. Several genera of the The violet-flowered Chinese wistaria phlox family have seeds that w^hen {Wisteria chinensis) is a stout climber wetted emit mucilage speedily in the with woody pods. The hard, rounded form of fine threads. The seeds in this seeds, when the pod opens, can fly 10 group do not become viscid until feet across a room. The native witch- wetted, so that they may be blown hazel {Hamamelis virginica) bears ex- about, when dry, until they reach a plosive capsular fruits. spot that is damp enough for them to Seed pods of many leguminous spe- exude mucilage and also to germinate. cies open explosively when ripe. The Another way in which viscid seeds large, thick pods of the West Indian are spread is to become attached to swordbean {Canavalia gladiata) snap dry leaves that the wind may carry oflf. open, and the seeds are thrown 10 to 20 feet. FORCEFUL dchiscence somedmes dis- The sandboxtree {Hura crepitans) is perses seed. known in the American Tropics for One example is the squirting-cu- the force that accompanies the burst- cumber {Ecballium elaterium), an an- ing of its round, 3-inch capsules, a nual vine whose fruit is an oblong force said to be enough to break open berry about 2 inches long. When a small wooden box in which a capsule thoroughly ripe, the fruit detaches was kept. itself from its peduncle. Increasing tension within the fruit breaks the TURTLES and tortoises often eat tissue, weakened at the point of de- fleshy fruits. The box turtle of the 86 YEARBOOK OF AGRICULTURE 1961 Eastern States feeds on wild strawber- boos {Melocanna baccifera)^ has hard, ries and other succulent fruits, and the woody seeds 4 inches long and nearly seeds pass uninjured through its di- 2 inches in diameter. gestive system. Lizards, particularly the larger ones that are found in the Tropics, feed freely on all sorts of fruits, especially those of certain cactuses. They also disperse the seeds effectively. Many freshwater fish feed on vegeta- tion, including fruits of water plants like waterlilies, and may swim for long ^^ distances before expelling the seeds. The ability of some fishes to pass over- land, usually through wet grass, from one body of water to another, is by no means uncommon, especially in some parts of the Tropics. Seeds are dis- persed in their travels. One curious method of seed dis- persal was mentioned by Charles Darwin in his Origin of Species. Herons and other birds, he reported, have eaten fish in whose stomachs were viable seeds of the yellow waterlily. In this way the herons often carried the A halj-shrubhyplant, Uncarina pcltata, hears a capsule. The long, slender processes are lerminaled seeds many miles from their source. ivilk four-winged barbs that cling to the hide or Land crabs, which feed on fallen jur of passing aniinals. fruits, have increased in this way the distribution of the Malayan legumi- nous tree known as Inocarpus edulis. The large garden snail in England has A native oak [Quercus corrúgala) been responsible for the dispersal of in southern Mexico bears enormous strawberries by eating the fruits. acorns with brown, wooly cups nearly The digestive tract of earthworms 2.5 inches across. The scales arc has been found, on dissection, to con- modified into concentric rings. A rel- tain a very wide variety of small seeds. ative of our well-known catalpa that grows in India (Oroxjlon indicum) is a SEEDS and seedlike fruits often are tree with flat pods 3 feet long, filled unusual and bizarre. with delicate, silky-papery, winged Probably the largest seed known seeds about 3 inches wide. among the flowering plants is the two- The bizarre capsule of the unicorn lobed seed of the so-called double plant of the Gulf States {Marlynia coconut (Lodoicea maldivica), a tall, kmisiana) resembles a large humming- handsome palm native in the Seychelle bird with two long, slender, upright Islands. One of them may weigh about tail feathers. These appendages have 40 pounds and be more than a foot small recurved points, which readily long and nearly 8 inches thick. attach the capsule to the fur of passing- Among the smallest known seeds arc animals or to a person's clothing. those of Siriga, which we discussed A similar method of dispersal is em- earlier, and certain orchid seeds. ployed by the Malagasy plant Uncarina Cuzco corn, from Peru, has large, pellaia, whose dry fruits, 3 inches in flat kernels nearly an inch wide. diameter, have numerous long, slender Another grass, one of the Indian bam- bristles, each terminated by four small, PLANTS MUST DISPERSE THEIR SEEDS 87 recurved hooks. One of these fruits at- It is highly important therefore that tached to fur or clothing is very hard all imported seeds, whether crop or to dislodge. weed, be correctly identified and eval- One of the Chinese watcrchestnuts uated before planting. {Trapa bicornis) has blackish fruits 3 inches across that closely resemble a THE IDENTIFICATION of seeds and bull's head, with two stout, curved, seed like fruits usually is based on ex- sharp-pointed horns. These fruits float ternal morphological features, such as for some distance before sinking to the shape, size, color, and surface con- bottom of the shallow river or pond, figuration or texture. Sometimes the where they may germinate. internal anatomy of the seed—the size The dipterocarps (Dipterocarpus)^ tall and position of the embryo or the trees from tropical Asia, are a source nature of the endosperm, for ex- of the commercial gurjun balsam. ample—furnishes useful clues to its Their fruits are small and globular and identity. have a persistent calyx. Two of the For seed identification of special sepals become greatly elongated up to groups, particular attention is paid to 7 inches long, and the other three re- the features that are characteristic of main short. The elongated, winglikc the group. For example, in determin- sepals enable the fruits to be wind ing species of the genus Cucúrbita, propelled for long distances. which includes pumpkins, squashes, and cushaws, special attention is paid THE RECEIPT of a shipment of cab- to the shape of the hilum (seed scar), bage seed from Russia in February the character and color of the seed 1898 marked the beginning of a con- margin, and the color of the seed face. tinuing program of plant introduction The identification of seeds of the by the Department of Agriculture, genus Pkaseolus, the cultivated beans, which collects plant materials, mostly takes into account the position, shape, as seeds, from all parts of the world for and size of the hilum, the nature of the experimental purposes. caruncle and micropyle, the nature The introductions are received from and color of the seedcoat, and the the Department's agricultural ex- nature of the parahilum, which is a plorers, foreign institutions, and other small area next to the hilum and is sources. They usually represent special characterized by tw^o small tubercules. strains or varieties of existing crop Seeds of two species of Hibiscus, the plants, or they may be wild relatives kenaf {H. cannabinus) and the roselle of cereals, forage plants, fruit, vege- {H. sabdariffa), both of economic im- tables, fiber plants, oil-yielding plants, portance, are almost alike, except that and plants for special projects. glossy, pale-brown spots occur on the Seeds of weeds may come into the surface of H. cannabinus. United States with imported crop Seeds of the mimosa family (Mi- seeds and on ships and airplanes. Most mosaceae), with one or two exceptions, of the noxious weeds in this country are easily separated from the seeds of were introduced from foreign sources other legumes by a horseshoe-shaped in this manner. Familiar examples are design on the seed faces. A continuous field bindweed (Convolvulus arvensis) elliptic or oval design on the seed faces and Canada thistle (Cirsium arvense). would place the seed in the family Some kinds of plants that are not Caesalpiniaceae. important weeds in their native land sometimes become extremely objec- A SEED HERBARIUM is essential for tionable under certain conditions in reference in identifying seeds, since parts of this country—as, for example, published descriptions of plants rarely giant foxtail {Setaria faberi) and St.- include the necessary morphological Johns-wort {Hypericum perjoratum). details of the seed and mature seeds 88 YEARBOOK OF AGRICULTURE 1061 are usually not present on specimens in plant herbariums. Newly introduced plant materials frequently must be identified promptly in order to be handled effectively. Life Processes of the The Department of Agriculture maintains a large general seed herbar- ium at the Plant Industry Station at Living Seed Beltsville, Md,, consisting not only of seeds, ranging in size up to 2 inches or R. G. STANLEY AND W. L. BUTLER more in diameter, but also seedlike fruits and certain types of dry fruits. The herbarium is used chiefly for identifying or checking the identi- THE EMBRYO in a seed draws on its en- fication of newly introduced plant dosperm for the nutrients it needs to materials. germinate and grow. A delicate bal- Another large seed herbarium, at ance of internal conditions regulates the Agricultural Research Center, its life processes. Beltsville, that consists mostly of actual The living seed is able to incorpo- and potential weeds and seeds of crop rate small molecules and simple sub- plants, is used mainly for identifica- stances—such as glucose, phosphorus, tions in carrying out the provisions of and sulfur—into complex , chemical the Federal Seed Act. units of a cell. These organized parts Together, these seed herbariums are the cell wall and the protoplasm, total about 100 thousand samples, which contains the cell nucleus. En- which come from all parts of the world. zymes act as the go-between in these More than 250 plant families are rep- conversions and building processes. resented, with 17 thousand species. The energy for this work comes from These herbariums may be used by the breakdow^n, or catabolism, of some anyone who cares to consult them. of the cclPs chemical components, usu- Some persons have learned that the ally by combining them with oxygen in study of seeds is an absorbing and prof- the process called respiration. itable hobby. It involves little expense Most of the seed components from and a small amount of time and energy. which the enzymes of the protoplasm It is a field in which there are satisfying and cell walls form new cells can be and practical returns. For the farmer classed as proteins, fats, carbohy- or nurseryman, a collection of seeds of drates, organic acids, and amino acids. authentically identified plants is of Thus the seed lives as long as its out- value in checking new or little-known side environment (against which its seed materials. The introduction of seedcoat helps protect it) and internal new and possibly dangerous weeds environment maintain active enzymes could very well be forestalled if au- and a good balance of chemical sub- thentic samples of them were on hand stances. Only under these conditions for comparison. Small glass vials and can the embryo, the result of the fusion gummed labels from a pharmacy are of the sperm and egg nuclei, produce ideal for filing small samples of seeds. new cells and a healthy plant. Moisture, temperature, and gases, PAUL G. RUSSELL is a collaborator in particularly carbon dioxide and oxy- the New Crops Research Branchy Agricul- gen, can afi'ect markedly the enzymes tiiral Research Service. Before retiring in and chemical components of the living ig^g, he was a botanist in the same branch. seed. Fungi, insects, bacteria, chem- ALBINA F. Mv^ihwas a seed technologist icals, or light can diminish or destroy in the Seed Branch, Grain Division, before the seed's power to germinate. Many she retired in ig6o. oí the same factors, in the right con-