The Project Gutenberg EBook of Seed Dispersal, by William J. Beal This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org Title: Seed Dispersal Author: William J. Beal Release Date: July 31, 2008 [EBook #26158] Language: English Character set encoding: ISO-8859-1 *** START OF THIS PROJECT GUTENBERG EBOOK SEED DISPERSAL *** Produced by Ron Swanson SEED DISPERSAL BY W. J. BEAL, M.S., PH.D. PROFESSOR OF BOTANY AND FORESTRY IN MICHIGAN AGRICULTURAL COLLEGE GINN & COMPANY BOSTON · NEW YORK · CHICAGO · LONDON COPYRIGHT, 1898 BY WILLIAM J. BEAL ALL RIGHTS RESERVED 36.11 The Athenæum Press GINN & COMPANY · PROPRIETORS · BOSTON · U.S.A. PREFACE. This little book is prepared with the thought of helping young botanists and teachers. Unless the reader has followed in detail, by actual experience, some of the modes of plant dispersion, he can have little idea of the fascination it affords, or the rich rewards in store for patient investigation. A brief list of contributions to the subject is given; but, with very few exceptions, the statements here made, unless otherwise mentioned in the text, are the results of observations by the author. I am under obligations for suggestions by my colleague, Prof. W. B. Barrows; my assistant, Prof. C. F. Wheeler; and a former instructor of botany, L. H. Dewey, now of the United States Department of Agriculture. B. O. Longyear, instructor in botany, with very few exceptions, has made the drawings. W. J. BEAL. AGRICULTURAL COLLEGE, MICHIGAN. CONTENTS. CHAPTER I.—HOW ANIMALS GET ABOUT. 1. Most of the larger animals move about freely 2. Some animals catch rides in one way or another CHAPTER II.—PLANTS SPREAD BY MEANS OF ROOTS. 3. Fairy rings 4. How nature plants lilies 5. Roots hold plants erect like ropes to a mast 6. How oaks creep about and multiply CHAPTER III.—PLANTS MULTIPLY BY MEANS OF STEMS. 7. Two grasses in fierce contention 8. Runners establish new colonies 9. Branches lean over and root in the soil 10. Living branches snap off and are carried by water or wind CHAPTER IV.—WATER TRANSPORTATION OF PLANTS. 11. Some green buds and leaves float on water 12. Fleshy buds drop off and sprout in the mud 13. Seeds and fruits as boats and rafts 14. Bits of cork around the seeds prevent them from sinking 15. An air-tight sack buoys up seeds 16. Fruit of basswood as a sailboat, and a few others as adapted to the water CHAPTER V.—SEEDS TRANSPORTED BY WIND. 17. How pigweeds get about 18. Tumbleweeds 19. Thin, dry pods, twisted and bent, drift on the snow 20. Seeds found in melting snowdrifts 21. Nuts of the basswood carried on the snow 22. Buttonwood balls 23. Seeds that tempt the wind by spreading their sails 24. Why are some seeds so small? 25. Seeds with parachutes 26. A study of the dandelion 27. How the lily sows its seeds 28. Large pods with small seeds to escape from small holes 29. Seeds kept dry by an umbrella growing over them 30. Shot off by wind or animal 31. Seed-like fruits moved about by twisting awns 32. Grains that bore into sheep or dogs or the sand 33. Winged fruits and seeds fall with a whirl 34. Plants which preserve a portion of their seeds for an emergency CHAPTER VI.—PLANTS THAT SHOOT OFF THEIR SPORES OR SEEDS. 35. Dry pods twist as they split open and throw the seeds 36. A seed case that tears itself from its moorings CHAPTER VII.—PLANTS THAT ARE CARRIED BY ANIMALS. 37. Squirrels leave nuts in queer places and plant some of them 38. Birds scatter nuts 39. Do birds digest all they eat? 40. Color, odor, and pleasant taste of fruits are advertisements 41. The meddlesome crow lends a hand 42. Ants distribute some kinds of seeds 43. Cattle carry away living plants and seeds 44. Water-fowl and muskrats carry seeds in mud 45. Why some seeds are sticky 46. Three devices of Virginia knotweed 47. Hooks rendered harmless till time of need 48. Diversity of devices in the rose family for seed sowing 49. Grouse, fox, and dog carry burs 50. Seeds enough and to spare CHAPTER VIII.—MAN DISPERSES SEEDS AND PLANTS. 51. Burs stick to clothing 52. Man takes plants westward, though a few migrate eastward CHAPTER IX.—SOME REASONS FOR PLANT MIGRATION. 53. Plants are not charitable beings 54. Plants migrate to improve their condition 55. Fruit grown in a new country is often fair 56. Much remains to be discovered BIBLIOGRAPHY SEED DISPERSAL. CHAPTER I. HOW ANIMALS GET ABOUT. 1. Most of the larger animals move about freely.—When danger threatens, the rabbit bounds away in long jumps, seeking protection in a hollow tree, a log, or a hole in the ground. When food becomes scarce, squirrels quickly shift to new regions. Coons, bears, skunks, and porcupines move from one neighborhood to another. When the thickets disappear and hunters abound, wild turkeys and partridges retreat on foot or by wing. When the leaves fall and the cold winds blow, wild geese leave the lakes in secluded northern homes, and with their families, reared during the summer, go south to spend the winter. Turtles swim from pond to pond or crawl from the water to the sand bank, where they lay and cover their eggs. Fishes swim up or down the creek with changing seasons, or seek deep or shallow water as their needs require. Beetles and butterflies, when young, crawl about for food and shelter, and when older use their wings in going long distances. These examples only serve to recall to mind what every boy or girl knows and has known ever since he can remember —that most animals move about whenever they want to, or whenever other animals will let them. 2. Some animals catch rides in one way or another.—Some small animals, like lice, ticks, and tiny spiders, walk slowly and only for short distances. If, because of scarcity of food, they are suddenly seized with the desire to move for a long distance, what are they to do? On such occasions ticks and lice watch quietly the first opportunity, catch on to the feet of birds or flying insects or other animals which may happen to come their way, and, like a boy catching on to a farmer's sleigh, ride till they get far enough, then jump off or let go, to explore the surrounding country and see whether it is fit to live in. If for some reason a spider grows dissatisfied and wants to leave the home spot, she climbs to the top of some object and spins out a fine, long web; this floats in the air, and after a while becomes so long and light that the wind will bear the thread and the spinner for a considerable distance, no one knows how far. These facts about lice and spiders show how wingless insects can go long distances without wings of their own. How is it with plants? The woods, fields, marshes, roadsides ever abound with interesting objects provided with strange devices waiting to be studied by inquisitive girls and boys in and out of school, and this finding out of nature's puzzles is one of the deepest pleasures of life. How quickly a mould attacks and creeps or spreads through a basin of berries every one knows. The mould is as much a plant as the bush that produced the berries; it comes from a small spore, which takes the place of a bud or sprout or seed. The decay of a tree begins where a limb or root has been injured, and whether the timber is living or dead, this decay results from the growth of some one or more low forms of plant life which enter the timber in certain places and slowly or quickly penetrate and affect other portions more or less remote. CHAPTER II. PLANTS SPREAD BY MEANS OF ROOTS. 3. Fairy rings.—Several low forms of plant life, such as Marasmius oreades, Spathularia flavida, and some of the puffballs, start in isolated spots in the grass of a lawn or pasture, and spread each year from a few inches to a foot or more in every direction, usually in the form of a circle; at the end of fifteen years some of these circles acquire a diameter of fifteen to twenty feet or more. These are known as fairy rings. Before science dispelled the illusion they were believed to have been the work of witches, elves, or evil spirits, from which arose the name. Several kinds of lichens and mosses and the like, growing on the barks of trees, fence boards, and low ground, spread slowly in the manner of fairy rings. However, the spreading is not always a slow, creeping process, for sometimes these low plants spread over an incredible distance in a short space of time. In some instances they appear suddenly almost anywhere, and at any season of the year. They are all minute and exist in countless numbers, and their devices for securing wide dispersion are so various as to entitle them to first rank in this respect. Some send off spores with a sharp puff, as if shot from a little gun. Some of these spores float on water, and some are sticky and thus gain free rides. It is not at all improbable that some are carried by the winds across oceans and continents. It is well known that many of the lower species of plants are more widely distributed over the earth than most of the higher plants. Every cloud from a ripe puffball consists of thousands of spores started on the wings of the wind for an unknown journey. Their habits are not past finding out, but to examine them a person needs a good microscope. Most of them have no special common name, and with one or two exceptions further mention of the mode of distribution of this fascinating portion of plant life cannot here be made. In our botanic garden was planted a patch six feet across of what is known as Oswego tea, bee balm, or red-flowered bergamot, an interesting plant with considerable beauty. It grew well for a year, the next year it failed to some extent, and on the third most of the plants died, or nearly died, excepting the spreading portion all around the margin. This is a fairy ring of another type, and represents a very slow mode of travel. As further illustrations of this topic study common yarrow, betony, several mints, common iris, loosestrife, coreopsis, gill-over-the-ground, several wild sunflowers, horehound, and many other perennials that have grown for a long time without transplanting. The roots of plants are seldom much observed, because they are out of sight. In soft ground the roots of the common or black locust extend from twenty to forty feet in each direction, and almost anywhere along these roots buds may appear, and a shoot spring up and become a tree. This peculiarity is worth as much to locusts in the matter of spreading as though the parent trees were able to move about. A number of kinds of poplars and willows, ailanthus, some of the elms, ashes, sweet potatoes, milkweeds, Canada thistles, and others behave in a similar manner. Little bits of Canada-thistle root half an inch long may send forth buds, and each bud grow to be an independent plant. FIG. 1.—Buds and shoots sprouting from roots of the common locust. Roots have a peculiarity not usually known. They stretch out and crook about here and there, penetrating the crevices of the soil wherever there is the least chance, and the matured portions begin to shorten, reminding one somewhat of an angleworm when one end has been stepped on. By this shortening process the top or crown of a dandelion or plantain is pulled down beneath the surface of the ground. 4. How nature plants lilies.—Lilies grow from bulbs which are planted six inches beneath the surface. Do you know how nature plants them? A seed starts and becomes a small plant on the surface of the leaf mould or a little beneath; little roots push downward and to right and left; and later, after getting a good hold below with numerous branchlets, the slender roots shorten and tug away at the tiny bulb above, as much as to say, "Come down a little into mother earth, for cold winter is approaching and there will be danger from frost." The young bulb is drawn down an inch more or less, the slender roots perish with the growing year, but the bulb is preserved. The seedling was well planned; for while it had yet tender leaves during its first year, starch and protoplasm were stored up in the thickened scales of the bulb. During the second spring some of this food in store is used to send down another set of slender roots with the message to gather in more water, potash, phosphorus, nitrogen, and other substances to help grow a larger bulb. In late summer and autumn the new roots contract and pull away at the greater bulb, and down it goes into the ground another inch or so. I have a theory as to how it finally comes to be drawn down just deep enough and no more, but I will not venture to give it. This process is repeated from year to year till the proper depth is reached for preserving the full-grown bulb. And this is the way nature plants bulbs. In a similar manner young slender roots well anchored in the soil, at or near the close of the growing season, pull downward and outward large numbers of bulblets that form around a parent bulb of some kinds of leeks, tulips, star-of- bethlehem, globe hyacinth, and monkshood. The pull of the roots is much greater to one side than downward, because most of the longest roots extend sidewise. Marilaun reports that a certain lawn in Vienna was mown so frequently that tulips could not go to seed, but after twenty years, from a very few bulbs planted near each other, a space twenty paces in diameter was well covered by tulips. And this is one way tulips travel, slow and sure. 5. Roots hold plants erect like ropes to a mast.—Did you ever lift vines of cucumbers, squashes, and the like, where they had rooted at the joints, and observe how forlorn they looked after the operation, with leaves tipped over, unable to remain erect? While growing, the stem zigzags or winds about more or less, and thus enables it to hold the leaves erect; besides, the tendrils catch on to weeds and curl up tight, and the roots at the joints are drawn taut on each side after the manner mentioned above, and act like ropes to a mast to hold the stem in its place, and thus help to hold the leaf above erect. 6. How oaks creep about and multiply.—Oaks FIG. 2.—Small tree, "grub," of white oak many times killed back; finally dead at the middle and sprouting on the margins. come from acorns; everybody knows that. The nuts are produced in abundance, and those of the white oak send out pretty good tap roots on the same year they fall. Some of the nuts roll down the knoll or are carried about by squirrels or birds, as mentioned elsewhere. Let me tell you one thing that I discovered the white oaks were doing in the sand of the Jack-pine plains of Michigan. In dry weather the dead grass, sticks, and logs are often burned, which kills much or all that is growing above ground. In this way little maples, ashes, witch-hazels, willows, huckleberries, blackberries, sweet ferns, service berries, aspens, oaks, and others are often killed back, but afterward sprout up again and again, and, after repeated burnings, form each a large rough mass popularly known as a grub. The grubs of the oak are well known; the large ones weighing from 75 to 100 pounds each. To plow land where grubs abound requires a stout plow and several pairs of horses or oxen. A small white oak, after it has been many times killed to the ground, dies in the middle and sprouts at the margins, and finally the main root perishes, and two roots, with branches a little distance apart, support each a cluster of stems above ground. FIG. 3.—Grub, or remains of a white oak, doubtless at one time much like Fig. 2, but now decayed in the middle, including its main root; sprouting on the margins, farther and farther out after the tops were killed, to the ground. FIG. 4.—Grub, or remains of a white oak, still older than the one represented in Fig. 3. A hole appears where the tap root has rotted away. The right-hand portion is already dividing, and in time, if often killed back, we might find several distinct oaks as descendants from one acorn. There can be no doubt that young oak trees slowly move in this manner from one place to another. If in fifty years we have two distinct grubs or branches, three or four feet apart, where the connecting part has finally died out, I see no reason why in another fifty years each one of the two may not again have spread and divided, giving us at least four grubs, or clusters of sprouts, all originally coming from one acorn; and so the matter might go on. This is slow traveling, I admit, but there is nothing to hinder nature from taking all the time she wants. FIG. 5.—Part of a grub of white oak, still alive and spreading over the ground, the central portions dying, the margins alive and spreading. CHAPTER III. PLANTS MULTIPLY BY MEANS OF STEMS. 7. Two grasses in fierce contention.—In growing a lawn at the Michigan Agricultural College, a little Bermuda grass was scattered with June grass, and the struggle has been most interesting. In the spring and for six weeks in autumn, when moisture usually abounds and the weather is cool, June grass thrives and little else is seen. In the dry, hot weeks of July and August, June grass rests and the Bermuda, which continues to spread, assumes control of the lawn, with but little of the June grass in sight. Each struggles for possession and does the best it can, and to some extent one supplements the other, with the result that at all times from spring to fall there is a close mat of living green which delights the eye and is pleasant to the feet that tread upon it. In soft ground, with plenty of room, a bit of quick or quack grass, or Bermuda, will extend in a year three to five feet or more in one direction. FIG. 6.—Rootstock of quick grass which has grown through a potato, and in this way may be carried to another field or another farm. June grass, quick grass, Bermuda grass, redtop, and white clover, wherever opportunity offers, spread by means of jointed stems, creeping and rooting at every joint on the surface of the ground or a little way below. These are not roots at all, but true stems somewhat in disguise. Here may also be mentioned, as having similar habit, artichokes, peppermint, spearmint, barberry, Indian hemp, bindweed, toadflax, matrimony vine, bugle-weed, ostrich fern, eagle fern, sensitive fern, coltsfoot, St. John'swort, sorrel, great willow-herb, and many more. 8. Runners establish new colonies.—The spreading of strawberries by runners must be familiar to every observer. In 1894 a student reported that a wild strawberry plant in the botanic garden had produced in that year 1230 plants. Weeds were all kept away, the season was favorable, the soil sandy; but on one side, within a foot and a half, progress was checked by the presence of a large plant of another kind. The multiplication of this plant by seeds, in addition to that by runners, would have covered a still greater area of land. Other plants with runners much like the strawberry are: several kinds of crowfoot, barren strawberry, cinquefoil, strawberry geranium, and orange hawkweed. Plants of the star cucumber, one-seeded cucumber, grapes, morning-glories, and others, spread more or less over bushes or over the ground, and are thus enabled to scatter seeds in every direction. FIG. 7.—The runner of a strawberry plant. 9. Branches lean over and root in the soil.—A black raspberry grows fast in the ground and has to stay in one spot for life. It has neither legs, feet, nor wings, and yet it can travel. The bush takes deep root and spreads out its branches, which are sometimes ten feet or more in length; the tips of these branches curve over to the ground six feet away, and finally take root; from these roots new colonies are formed, five to twenty in a year from one bush. True, the old roots do not get far, and the new plants only get about six feet in one season, but they have made some progress. This is rather slow locomotion, you say; but let us look a little farther, remembering that a seed is a little plant packed ready for transportation. This second mode of spreading will be described on a future page. FIG. 8.—Plant of a black raspberry showing one branch (stolon) with several tips rooting. 10. Living branches snap off and are carried by water or wind.—Some trees and shrubs among the willows are called snap-willows, because their branches are very brittle; on the least strain from wind, rain, sleet, or snow, the smaller branches snap off near the larger branches or the main trunk, and fall to the ground. At first thought this brittleness of the wood might seem to be a serious defect in the structure of the tree or shrub, although they seem to produce branches enough for their own use. But the branches which are strewn all around after a storm often take root in the low ground where they fall; some of them are carried down stream by the current, and, lodging on the shore below, produce new trees or bushes. During the winter of 1895 and 1896 a group of seven white willows, near a brook on the campus of the Michigan Agricultural College, was at one time loaded with sleet. There was considerable snow on the ground, which, of course, was covered with an icy crust. In a little while the sleet melted from the fallen branches strewn about, and a moderate breeze then drifted the smallest of the twigs in considerable numbers over the icy snow. Some of these were found thirty rods distant from the parent trees—not down stream in the valley of the brook, but up the stream. Had not the low ground been covered with a dense growth of grass, some of these branches might have started new trees where the wind had left them.1 1 C. D. Lippincott believes that this is a provision of nature to dispose of the now unnecessary branchlets without leaving a knot. Plant World, Vol. I, p. 96. FIG. 9.—Branch of snap-willow rooting at one end. FIG. 10.—Portion of a branch of the cottonwood as it fell from the tree. The branches on slow-growing limbs of cottonwood and large-toothed aspen are much enlarged at the nodes, and at these places are brittle, often separating from the tree and breaking up into pieces. Under a small cottonwood were picked up a bushel or more of such limbs, all yet alive. These trees are common on low land, and, like snap-willows, the severed twigs may find a chance to grow on moist soil.2 2 The brittle branches of salix were noticed by the author in Bull. Torr. Bot. Club, Vol. IX (1883), p. 89. In a greenhouse a potted plant of Selaginella emiliana(?) was placed on the bench near the aisle, where it was often brushed by people in passing. Small branches, not being firmly attached, were frequently broken from the main plant and fell upon the moist sand, where they rooted in abundance. CHAPTER IV. WATER TRANSPORTATION OF PLANTS. FIG. 12.—Floating leaf of lake cress, Nasturtium lacustre, with a young plant growing from the base. 11. Some green buds and leaves float on water.—Loosely floating on slow streams of the northern states, in water not the purest, may often be found the common bladderwort, Utricularia vulgaris, producing in summer a few yellow flowers on each stem, rising from six to twelve inches above the water. The lax, leafy branches in the water are from six inches to a foot long. The leaves, or thread-like branches, are about half an inch long, more or less, and several times divided. FIG. 11.—A free branch and two buds of bladderwort. Scattered about are large numbers of flattened scales, or bladders, sometimes one-sixth of an inch long, which give the plant one of its names. For a long time the bladders were thought to serve merely as life-preservers; it was supposed that they were constructed to keep the plant from sinking to the bottom. In reality these bladders help preserve the plant in another sense, by catching and killing large numbers of minute animals, on which the plant lives in part. The tips of the stems at all times of the year are rather compact, made up of young leaves and stems, and in the middle of the summer, as well as at other times, many may be seen severed from the parent plant, floating in the water, ready to accept the assistance of any favorable current or breeze and start out for homes of their own to found new colonies. These olive- green tips, or buds, vary much in size, but the largest are the size of the end of one's little finger. Late in autumn or early winter, when cold threatens, the tender buds contract a little, and, having thus become heavier than water, slowly go to the bottom to spend the winter safely protected in the soft mud. All the plant perishes except these buds. With the lengthening days of spring the melting ice disappears, and genial sunshine gives notice to the dormant buds that it is safe to come out again. The buds begin to expand, become lighter than water, and are soon seen spreading out at the surface and producing branches and leaves. Ducks and other water-fowl not infrequently carry some of these wet buds sticking to their feathers or legs. In this connection the following plants may be examined from time to time: Lemna, Wolffia, Anacharis (Elodea), Myriophyllum, Cabomba, and several species of Potamogeton. I have seen the leaves of lake cress, Nasturtium lacustre, often spontaneously separate from the stem, possibly carrying at the base the rudiments of a small bud, which draws on the floating leaf for nourishment and produces a small plant near its base. These plants, floated and nourished by the mother leaf, may drift down a creek or across a pond and establish new settlements. In a similar manner behave leaves of the following, and perhaps others: Cardamine pratensis, horse-radish, celandine, some water lilies, and other plants not grown in wet land. Gardeners often propagate certain species by placing leaves on wet sand or mud, when buds spring from the margins of the leaves or from some other portion. One of the buttercups, Ranunculus multifidus, and very likely others, spread over the mud by producing runners, much after the manner of a strawberry plant. If, as in case of a freshet, the plants should be covered with water, they show their enterprise by taking advantage of the "tide"; some of the runners are quickly severed, and are then at liberty to go as they please. 12. Fleshy buds drop off and sprout in the mud.—One of the loosestrifes, Lysimachia stricta, a plant growing in bogs, besides reproducing itself by rootstocks and seeds, bears fleshy buds half an inch long, which separate from the stems and take root in the mud near the parent plant, or often float to another spot. The buds on the stems of Cicuta bulbifera develop into small bulbs, which readily separate from the plant. They then float on the water and produce new plants. The tiger lily also produces bulblets, which scatter about and promptly take root. Every person of good understanding must have heard or read about seeds carried by ocean currents or transported by lake, pond, creek, or by muddy current, during, and after, a shower of rain; in most of these the wind is also a prominent factor. Many seeds and fruits, in some cases parts, and even the whole, of plants seem to be purposely designed for this mode of travel, while an innumerable host of others occasionally make use of it, although it may seem from their structure and place of growth that they were made especially to be transported by the wind or by some animal. As has been seen in examples previously mentioned, one portion of a plant is transported in one way, and another portion by one or two other methods. FIG. 13.—Branch of loosestrife bearing tuber bulblets. FIG. 14.—One of the tubers enlarged. 13. Seeds and fruits as boats and rafts.—An excellent place in which to begin investigating this part of the subject is to pay a visit to the flats of a FIG. 15.—Fruit of bladder nut with three tight cells. FIG. 16.—Shriveled wild grapes overlooked by birds, now ready to float on water, and a clean seed not able to float. FIG. 18.—Fruit of Asa-Gray sedge with an inflated sack about it. FIG. 19.—Fruit of Carex communis, an upland sedge, that readily sinks when placed in water; the sack fits closely. creek or river late in autumn or in the spring, after the water has retired to its narrow channel, and examine piece after piece of the rubbish that has been lodged here and there against a knoll or some willows, a patch of rushes or dead grass. We are studying the different modes by which plants travel. In the driftwood may be found dry fruits of the bladder nut, brown and light, an inch and a half in diameter. See how tough they are; they seem to be perfectly tight, and even if one happens to have a hole punched in its side, there are probably two cells that are still tight, for there are three in all. Within are a few seeds, hard and smooth. Why are they so hard? Will it not be difficult for such seeds to get moist enough and soft enough to enable them to germinate? The hard coats enable the seeds to remain uninjured for a long time in the water, in case one or two cells of the papery pods are broken open; and after the tough pod has decayed and the seeds have sunken to the moist earth among the sticks and dead leaves, they can have all the time they need for the slow decay of their armor. Sooner or later a tiny plant is likely to appear and produce a beautiful bush. Engineers are boasting of their steel ships as safe and not likely to sink, because there are several compartments each in itself water-tight. In case of accident to one or two chambers, the one or two remaining tight will still float the whole and save the passengers. I wonder if the engineers have not been studying the fruit of the bladder nut? But this is not all. Many of the dry nuts hang on all winter, or for a part of it, rattling in the wind, as though loath to leave. Some of them are torn loose, and in winter there will be a better chance than at any other time for the wind to do the seeds a favor, especially when there is snow on the ground, for then they will bound along before the breeze till something interrupts them. Here among the rubbish are some shriveled wild grapes also. As we shall see elsewhere, their best scheme is to be eaten by certain birds, which do not digest their bony seeds; but in case some of them are left there is another mode of travel, not by wings of a bird, but by floating on water. Clean grape seeds sink at once, but covered by the dry skin and pulp, they float. In a similar manner the dry seeds of several dogwoods are eaten for the pulp by birds, but in case any are left they behave after the manner of grapes. 14. Bits of cork around the seeds prevent them from sinking.—Narrow-leaved dock is a prominent weed, and is especially at home on river bottoms and on low land that is flooded once in a while. Did you ever wonder what could be the object of a round, spongy tubercle on the outside of each of these sepals which hold the ripened seed closely? I did not know their use for a long time, but now think I have discovered their meaning. They are not exactly life-preservers, but the next thing to it. The naked, seed-like fruit, the shape of the fruit of buckwheat, sinks at once when free from everything else, but with the dry calyx still attached, it floats with the stream. FIG. 17.—Fruit and adherent calyx of narrow-leaved dock; a cross section and a naked, seed-like fruit (enlarged). 15. An air-tight sack buoys up seeds.—Here are several dry fruits of sedges—plants looking considerably like grasses. There are a good many kinds, and most of them grow in wet places. The seed-like fruit of those we examine are surrounded each by a sack which is considerably too large for it, as one would be likely to say, but in reality it serves to buoy the denser portion within, much after the plan of the bladder nut. In some instances the sack is rather small, but a corky growth below the grain helps to buoy it on water. Sedges that grow on dry land usually have the sack fitted closely, instead of inflated, and the whole mass sinks readily in water. Now we see the probable reason why the sack is inflated in some species of sedges and not in others. Here are some small, seed-like fruits, achenes, not likely to be recognized by every one. They belong to the arrowhead, Sagittaria, found in shallow ponds or slow streams. They are flattened, and on one edge, or both, and at the apex is a spongy ridge. Very likely, by this time, the reader has surmised that this serves the purpose of a raft to float the small seed within, which would sink at once if separated from the boat that grew on its margins. In this connection may be studied achenes of water plantain, Alisma, bur reed, cat-tail flag, arrow grass, burgrass, numerous pondweeds, several buttercups, the hop, nettles, wood nettle, false nettle, cinquefoil, avens, ninebark, buttonbush, and in fact a large number and variety of plants usually found on river bottoms. FIG. 20.—Seed-like fruit of arrowhead with corky margins to float on water. FIG. 21.—Seed-like fruit of bur reed with corky lining ready to float on water, and a naked seed, such as sinks promptly. FIG. 22.—Grains of lyme grass with two corky empty glumes attached, which serve as a raft. FIG. 23.—Seed of milkweed with a corky margin enabling it to float; a seed with such margin removed sinks at once. FIG. 24.—Cranberry containing an air space which helps it to float. One of the lyme grasses, Elymus Virqinicus, is a stiff, short grass, growing along streams. Each spikelet with its chaff adheres to two empty glumes, stout, thick, and spongy, which make a safe double boat for transportation down stream whenever the water is high enough. The grains of rice-cut grass, grown in ditches and spring brooks, sink if separated, but in the chaff, as they fall when ripe, they are good floaters. In the driftwood, which we still have under consideration, are some fruits of maple, beech, oak, tulip tree, locust, and basswood. Maples are well scattered by the wind, but these seed-like fruits have taken to the water, and a few still retain vitality. An acorn, while yet alive, sinks readily, and is not suited for water navigation, unless by accident it rides on some driftwood. The fruits of the tulip tree, locust, and basswood behave well on the water, as though designed for the purpose, though we naturally, and with good reason, class them with plants usually distributed by wind. 16. Fruit of basswood as a sailboat, and a few others as adapted to the water.—In spring, when the bracts and fruits of the basswood are dry and still hanging on the tree, if a quantity of them are shaken off into the water which overflows the banks of a stream, many of these, as they reach the water, will assume a position as follows: The nuts spread right and left and float; the free portion of the bract extends into the water, while the portion adhering to the peduncle rises obliquely out of the water and serves as a sail to draw along the trailing fruit. After sailing for perhaps fifteen minutes, the whole bract and stem go under water, the nuts floating the whole as they continue to drift with the wind. Noticeable among seeds in the flood wood are some of the milkweeds, which every one would say at a glance were especially fitted for sailing through the air, aided by their numerous long, silky hairs. These hairs are no hindrance to moving by water. I discovered one little thing in reference to the seed which makes me think the Designer intended it should to some extent be carried by water. The flat seed has a margin, or hem, which must be an aid to the wind in driving it about; but this margin is thickened somewhat by a spongy material. With the margin it floats, without it the seed sinks in fresh water. A few cranberries were found in the driftwood. These contain considerable air in the middle, near where the seeds are placed, as though the air was intended to support them on top of water. These berries are colored and edible—qualities that attract the birds. And here we find in several places the bulblets of a wild garlic, Allium Canadense, which grows on the river bottom. These bulblets are produced on top of the stem with the flowers, and float on the water. The seeds of the white water lilies, and yellow ones also, by special arrangement float about on the water with the current or the wind. The coffee tree grows rather sparingly along some of the streams, and on moist land as far north as Clinton County, Michigan. The stout, hard pods are three to four inches long, one and one-quarter to one and one-half inches wide, and one-half inch thick. The very hard seeds are surrounded with sweet pulp, which most likely made it an inducement for some of our native animals to devour them and thus transport the undigested seeds to remote localities. The pods often remain on the trees all winter, and when dry, will float on the water of overflowed streams without any injury resulting to the hard seeds. By themselves the seeds sink at once. CHAPTER V. SEEDS TRANSPORTED BY WIND. 17. How pigweeds get about.—In winter we often see dead tops of lamb's-quarters and amaranths—the smooth and the prickly pigweeds—still standing where they grew in the summer. These are favorite feeding grounds for several kinds of small birds, especially when snow covers the ground. Many of the seeds, while still enclosed in the thin, dry calyx, and these clustered on short branches, drop to the snow and are carried off by the wind. Notwithstanding the provision made for spreading the seeds by the aid of birds and the wind, the calyx around each shiny seed enables it to float also; when freed from the calyx, it drops at once to the bottom. Many kinds of dry fruits and seeds in one way or another find their way during winter to the surface of the ice- covered rivers. When the rivers break up, the seeds are carried down stream, and perhaps left to grow on dry land FIG. 27.—Two views of a half-pod of common locust, dry, twisted, and bent, ready for a breeze. after the water has retired. Most of the commonest plants, the seeds of which are usually transported by water, are insignificant in appearance and without common names, or with names that are not well understood. This is one reason for omitting the description of others which are ingeniously fitted in a great variety of different ways for traveling by water. 18. Tumbleweeds.—Incidentally, the foregoing pages contain some account of seeds and fruits that are carried by the aid of wind, in connection with their distribution by other methods; but there are good reasons for giving other examples of seeds carried by the wind. There is a very common weed found on waste ground and also in fields and gardens, which on good soil, with plenty of room and light, grows much in the shape of a globe with a diameter of two to three feet. It is called Amaranthus albus in the books, and is one of the most prominent of our tumbleweeds. It does not start in the spring from seed till the weather becomes pretty warm. The leaves are small and slender, the flowers very small, with no display, and surrounded by little rigid, sharp-pointed bracts. When ripe in autumn, the dry, incurved branches are quite stiff; the main stem near the ground easily snaps off and leaves the light ball at the mercy of the winds. Such a plant is especially at home on prairies or cleared fields, where there are few large obstructions and where the wind has free access. The mother plant, now dead, toiled busily during the heat of summer and produced thousands of little seeds. The best portion of her substance went to produce these seeds, giving each a portion of rich food for a start in life and wrapping each in a glossy black coat. Now she is ready to sacrifice the rest of her body to be tumbled about, broken in pieces, and scattered in every direction for the good of her precious progeny, most of whom will find new places, where they will stand a chance the next summer to grow into plants. Sometimes the winds are not severe enough or long enough continued, and these old skeletons are rolled into ditches, piled so high in great rows or masses against fences that some are rolled over the rest and pass on beyond. Occasionally some lodge in the tops of low trees, and many are entangled by straggling bushes. In a day or two, or in a week, or a month, the shifting wind may once more start these wrecks in other directions, to be broken up and scatter seeds along their pathway. During the Middle Ages in southern Egypt and Arabia, and eastward, a small plant, with most of the peculiarities of our tumbleweed just described, was often seen, and was thought to be a great wonder. It was called the "rose of Jericho," though it is not a rose at all, but a first cousin to the mustard, and only a small affair at that, scarcely as large as a cabbage head. A number of other plants of this habit are well known on dry plains in various parts of the world; one of the most prominent in the northern United States is called the Russian thistle, which was introduced from Russia with flaxseed. In Dakota, often two, three, or more grow into a community, making when dry and mature a stiff ball two to three feet or more in diameter. FIG. 25.—Mature dry plant of Russian thistle as a tumbleweed. (One-seventh natural size.) One of our peppergrasses, Lepidium intermedium, sometimes attains the size and shape of a bushel basket; when ripe, it is blown about, sowing seeds wherever it goes. The plants of the evening primrose sometimes do likewise, also a spurge, Euphorbia [Preslii] nutans, a weed a foot to a foot and a half high. Low hop clover, an annual with yellow flowers, which has been naturalized from Europe, has developed recently on strong clay land into a tumbleweed six inches in diameter. The tops of old witch grass, Panicum capillare, and hair grass, Agrostis hyemalis, become very brittle when ripe, and snap from the parent stem and tumble about singly or in masses, scattering seeds by the millions. I have seen piles of these thin tops larger than a load of hay where they had blown against a grove of trees, and in some cases many were caught in the tops of low trees. FIG. 26.—The top of old witch grass as a tumbleweed. (Reduced two thirds.) Bug seed and buffalo bur are tumbleweeds. In autumn the careful observer with an eye to this subject will be rewarded by finding many other plants that behave more or less as tumbleweeds. Especially is this the case on prairies. These are annuals, and perish at the close of the growing season. There are numerous other devices by which seeds and fruit secure transportation by the wind. 19. Thin, dry pods, twisted and bent, drift on the snow.—The common locust tree, Robinia Pseudacacia, blossoms and produces large numbers of thin, flat pods, which remain of a dull color even when the seeds are ripe. The pods of the locust may wait and wait, holding fast for a long time, but nothing comes to eat them. They become dry and slowly split apart, each half of the pod usually carrying every other seed. Some of the pods with the seeds still attached are torn off by the wind and fall to the ground sooner or later, according to the force of the wind. Each half-pod as it comes off is slightly bent and twisted, and might be considered a "want-advertisement" given to the wind: "Here I am, thin, dry, FIG. 29.—(a) Lax stem, supporting (b) fruit of the buttonwood, or sycamore; (c) a single fruit separated, ready for the wind or water. light and elastic, twisted and bent already; give me a lift to bear these precious seeds up the hill, into the valley, or over the plain." And the wind is sure to come along, a slight breeze to-day tossing the half-pod a few feet, leaving it perhaps to be again and again moved farther forward. The writer has seen these half-pods transported by this means more than a block. But many of the pods stick to the limbs till winter comes. Then a breeze tears off a few pods and they fall on the snow, which has filled up all the crevices in the grass and between the dead leaves and rubbish. Each half-pod, freighted with every other seed, is admirably constructed; like an ice boat, it has a sail always spread to the breeze. In this way there is often nothing to hinder some of the seeds from going a mile or two in a few minutes, now and then striking some object which jars off a seed or two. The seeds are very hard, and no doubt purposely so, that they may not be eaten by insects or birds; but once in moist soil, the covering slowly swells and decays, allowing the young plant to escape. Thus the locust seeds are provided with neither legs, wings, fins, nor do they advertise by brilliant hue and sweet pulp; but they travel in a way of their own, which is literally on the wings of the wind. 20. Seeds found in melting snowdrifts.—It will interest the student of nature to collect a variety of seeds and dry fruits, such as can be found still on the trees and other plants in winter, and try some of them when there is snow on the ground and the wind blows, to see how they behave. Again, when the first snow banks of the early winter are nearly gone, let him collect and melt a quantity of snow and search for seeds. By this means he can see, as he never saw before, how one neighbor suffers from the carelessness of another. 21. Nuts of the basswood carried on the snow.—Here are some notes concerning the distribution of the spherical nuts of basswood. The small clusters of fruit project from a queer bract which remains attached before and after falling from the tree. FIG. 28.—Fruit and bract of basswood well adapted for moving before the wind on the snow. This bract, when dead, is bent near the middle and more or less twisted, with the edges curving toward the cluster of nuts. From two to five nuts about the size of peas usually remain attached till winter, or even a few till spring. This bract has attracted a good deal of attention, and for a long time everybody wondered what could be its use. We shall see. The cluster of nuts and the bract hang down, dangling about with the least breath of wind, and rattling on the trees because the enlarged base of the stem has all broken loose excepting two slender, woody threads, which still hold fast. These threads are of different degrees of strength; some break loose after a few hard gales, while others are strong enough to endure many gales, and thus they break off a few at a time. The distance to which the fruit can be carried depends on the form of the bract, the velocity of the wind, and the smoothness of the surface on which the fruit falls. When torn from the tree the twist in the bract enables the wind to keep the cluster rapidly whirling around, and by whirling it is enabled to remain longer suspended in the air and thus increase the chances for a long journey. In throwing some of these from a third-story window, it was found that a bract with no fruit attached would reach the ground sooner than a bract that bore from two to four solid nuts. The empty or unloaded bracts tumble and slide through the air endwise, with nothing to balance them or steady their descent, while the fruit on other bracts holds them with one side to the air, which prolongs their descent. The less a loaded bract whirls, the faster its descent, and the more a bract whirls when the wind blows, the farther it is carried. The bract that is weighted with a load of fruit acts as a kite held back by a string, and when in this position the wind lifts the whole as well as carries it along. Before snow had fallen in 1896, by repeated moves on a well-mowed lawn, fruit and bracts were carried about two hundred feet, while with snow on the ground the distance was almost unlimited, excepting where there were obstructions, such as bushes and fences. When there is a crust on the snow and a good wind, the conditions are almost perfect. Over the snow the wind drives the bracts, which drag along the branch of fruit much as a sail propels a boat. The curving of the edges of the bract toward the fruit enables the wind to catch it all the better, and to lift it more or less from the snow. With changes in the direction of the wind, there is an opportunity for the fruit of a single tree, if not too much crowded by others, to spread in all directions. After watching these maneuvers, no one could doubt the object of the bent bracts of the basswood, and as these vary much in length and width and shape on different trees, it would seem that perhaps nature is still experimenting with a view to finding the most perfect structure for the purpose. About one hundred and thirty paces west of the house in which I live stand two birch trees. One windy winter day I made some fresh tracks in the snow near my house, and within a few minutes the cavities looked as though some one had sprinkled wheat bran in them, on account of the many birch seeds there accumulated. Other fruits in winter can be experimented with, such as that of box elder, black ash, birches, tulip tree, buttonwood, ironwood, blue beech, and occasionally a maple. 22. Buttonwood balls.—Nature seems to have no end of devices for sowing seeds to advantage. Here is one which always interests me. The fruit of the buttonwood, or sycamore, which grows along streams, is in the form of balls an inch and a half in diameter. These balls grow on the tops of the highest branches, and hold on into winter or longer. The FIG. 30.—Fruit of willow-herb exposing seeds for distribution by the wind. stems are about two inches long, and soon after drying, through the action of the winds, they become very flexible, each resembling a cluster of tough strings. The slightest breeze mo...