SEED DISPERSAL

BYW. J. BEAL, M. S. , PH. D. PROFESSOR OF BOTANY AND FORESTRY IN MICHIGAN AGRICULTURAL COLLEGE

GINN & COMPANYBOSTON . NEW YORK . CHICAGO . LONDON

COPYRIGHT, 1898BY WILLIAM J. BEAL

ALL RIGHTS RESERVED36. 11

The Athenæum PressGINN & COMPANY . PROPRIETORS . BOSTON . U. S. A. 

PREFACE. 

This little book is prepared with the thought of helping youngbotanists and teachers. Unless the reader has followed in detail, by actual experience, some of the modes of plant dispersion, he canhave little idea of the fascination it affords, or the rich rewardsin store for patient investigation. 

A brief list of contributions to the subject is given; but, with veryfew exceptions, the statements here made, unless otherwise mentionedin 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 instructorof botany, L. H. Dewey, now of the United States Department ofAgriculture. B. O. Longyear, instructor in botany, with very fewexceptions, has made the drawings. 

W. J. BEAL. AGRICULTURAL COLLEGE, MICHIGAN. 

CONTENTS. 

CHAPTER I. --HOW ANIMALS GET ABOUT. PAGE 1. Most of the larger animals move about freely . . . . . . . . 1 2. Some animals catch rides in one way or another . . . . . . . 2

CHAPTER II. --PLANTS SPREAD BY MEANS OF ROOTS. 

 3. Fairy rings . . . . . . . . . . . . . . . . . . . . . . . . 4 4. How nature plants lilies . . . . . . . . . . . . . . . . . . 7 5. Roots hold plants erect like ropes to a mast . . . . . . . . 8 6. How oaks creep about and multiply . . . . . . . . . . . . . 8

CHAPTER III. --PLANTS MULTIPLY BY MEANS OF STEMS. 

 7. Two grasses in fierce contention . . . . . . . . . . . . . . 12 8. Runners establish new colonies . . . . . . . . . . . . . . . 13 9. Branches lean over and root in the soil . . . . . . . . . . 1410. Living branches snap off and are carried by water or wind . 15

CHAPTER IV. --WATER TRANSPORTATION OF PLANTS. 

11. Some green buds and leaves float on water . . . . . . . . . 1812. Fleshy buds drop off and sprout in the mud . . . . . . . . . 2013. Seeds and fruits as boats and rafts . . . . . . . . . . . . 2214. Bits of cork around the seeds prevent them from sinking . . 2415. An air-tight sack buoys up seeds . . . . . . . . . . . . . . 2516. Fruit of basswood as a sailboat, and a few others as adapted to the water . . . . . . . . . . . . . . . . . . 27

CHAPTER V. --SEEDS TRANSPORTED BY WIND. 

17. How pigweeds get about . . . . . . . . . . . . . . . . . . . 3018. Tumbleweeds . . . . . . . . . . . . . . . . . . . . . . . . 3119. Thin, dry pods, twisted and bent, drift on the snow . . . . 3520. Seeds found in melting snowdrifts . . . . . . . . . . . . . 3621. Nuts of the basswood carried on the snow . . . . . . . . . . 3722. Buttonwood balls . . . . . . . . . . . . . . . . . . . . . . 3923. Seeds that tempt the wind by spreading their sails . . . . . 4024. Why are some seeds so small? . . . . . . . . . . . . . . . . 4225. Seeds with parachutes . . . . . . . . . . . . . . . . . . . 4326. A study of the dandelion . . . . . . . . . . . . . . . . . . 4427. How the lily sows its seeds . . . . . . . . . . . . . . . . 4628. Large pods with small seeds to escape from small holes . . . 4729. Seeds kept dry by an umbrella growing over them . . . . . . 4830. Shot off by wind or animal . . . . . . . . . . . . . . . . . 5031. Seed-like fruits moved about by twisting awns . . . . . . . 5132. Grains that bore into sheep or dogs or the sand . . . . . . 5133. Winged fruits and seeds fall with a whirl . . . . . . . . . 5234. Plants which preserve a portion of their seeds for an emergency . . . . . . . . . . . . . . . . . . . . . . . . 54

CHAPTER VI. --PLANTS THAT SHOOT OFF THEIR SPORES OR SEEDS. 

35. Dry pods twist as they split open and throw the seeds . . . 5736. A seed case that tears itself from its moorings . . . . . . 59

CHAPTER VII. --PLANTS THAT ARE CARRIED BY ANIMALS. 

37. Squirrels leave nuts in queer places and plant some of them 6138. Birds scatter nuts . . . . . . . . . . . . . . . . . . . . . 6339. Do birds digest all they eat? . . . . . . . . . . . . . . . 6440. Color, odor, and pleasant taste of fruits are advertisements . . . . . . . . . . . . . . . . . . . . . 6541. The meddlesome crow lends a hand . . . . . . . . . . . . . . 6842. Ants distribute some kinds of seeds . . . . . . . . . . . . 6943. Cattle carry away living plants and seeds . . . . . . . . . 7044. Water-fowl and muskrats carry seeds in mud . . . . . . . . . 7145. Why some seeds are sticky . . . . . . . . . . . . . . . . . 7246. Three devices of Virginia knotweed . . . . . . . . . . . . . 7347. Hooks rendered harmless till time of need . . . . . . . . . 7448. Diversity of devices in the rose family for seed sowing . . 7649. Grouse, fox, and dog carry burs . . . . . . . . . . . . . . 7650. Seeds enough and to spare . . . . . . . . . . . . . . . . . 78

CHAPTER VIII. --MAN DISPERSES SEEDS AND PLANTS. 

51. Burs stick to clothing . . . . . . . . . . . . . . . . . . . 8052. Man takes plants westward, though a few migrate eastward . . 83

CHAPTER IX. --SOME REASONS FOR PLANT MIGRATION. 

53. Plants are not charitable beings . . . . . . . . . . . . . . 8454. Plants migrate to improve their condition . . . . . . . . . 8555. Fruit grown in a new country is often fair . . . . . . . . . 8556. Much remains to be discovered . . . . . . . . . . . . . . . 86

BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . 89

SEED DISPERSAL. 

CHAPTER I. HOW ANIMALS GET ABOUT. 

1. Most of the larger animals move about freely. --When dangerthreatens, the rabbit bounds away in long jumps, seeking protectionin a hollow tree, a log, or a hole in the ground. When food becomesscarce, squirrels quickly shift to new regions. Coons, bears, skunks, and porcupines move from one neighborhood to another. When thethickets disappear and hunters abound, wild turkeys and partridgesretreat on foot or by wing. When the leaves fall and the cold windsblow, wild geese leave the lakes in secluded northern homes, and withtheir families, reared during the summer, go south to spend the winter. Turtles swim from pond to pond or crawl from the water to the sandbank, where they lay and cover their eggs. Fishes swim up or downthe creek with changing seasons, or seek deep or shallow water astheir needs require. Beetles and butterflies, when young, crawl aboutfor food and shelter, and when older use their wings in going longdistances. 

These examples only serve to recall to mind what every boy or girlknows and has known ever since he can remember--that most animalsmove about whenever they want to, or whenever other animals will letthem. 

2. Some animals catch rides in one way or another. --Some small animals, like lice, ticks, and tiny spiders, walk slowly and only for shortdistances. If, because of scarcity of food, they are suddenly seizedwith 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 whichmay happen to come their way, and, like a boy catching on to a farmer'ssleigh, ride till they get far enough, then jump off or let go, toexplore the surrounding country and see whether it is fit to livein. If for some reason a spider grows dissatisfied and wants to leavethe home spot, she climbs to the top of some object and spins outa fine, long web; this floats in the air, and after a while becomesso long and light that the wind will bear the thread and the spinnerfor a considerable distance, no one knows how far. These facts aboutlice and spiders show how wingless insects can go long distanceswithout wings of their own. 

How is it with plants? The woods, fields, marshes, roadsides everabound with interesting objects provided with strange deviceswaiting to be studied by inquisitive girls and boys in and out ofschool, and this finding out of nature's puzzles is one of the deepestpleasures of life. 

How quickly a mould attacks and creeps or spreads through a basinof berries every one knows. The mould is as much a plant as the bushthat produced the berries; it comes from a small spore, which takesthe place of a bud or sprout or seed. The decay of a tree begins wherea limb or root has been injured, and whether the timber is livingor dead, this decay results from the growth of some one or more lowforms of plant life which enter the timber in certain places and slowlyor 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 _Marasmiusoreades_, _Spathularia flavida_, and some of the puffballs, startin isolated spots in the grass of a lawn or pasture, and spread eachyear from a few inches to a foot or more in every direction, usuallyin the form of a circle; at the end of fifteen years some of thesecircles acquire a diameter of fifteen to twenty feet or more. Theseare known as fairy rings. Before science dispelled the illusion theywere 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 barksof trees, fence boards, and low ground, spread slowly in the mannerof fairy rings. 

However, the spreading is not always a slow, creeping process, forsometimes these low plants spread over an incredible distance in ashort space of time. In some instances they appear suddenly almostanywhere, and at any season of the year. They are all minute and existin countless numbers, and their devices for securing wide dispersionare so various as to entitle them to first rank in this respect. Somesend off spores with a sharp puff, as if shot from a little gun. Someof these spores float on water, and some are sticky and thus gainfree rides. It is not at all improbable that some are carried by thewinds across oceans and continents. 

It is well known that many of the lower species of plants are morewidely distributed over the earth than most of the higher plants. Every cloud from a ripe puffball consists of thousands of sporesstarted on the wings of the wind for an unknown journey. Their habitsare not past finding out, but to examine them a person needs a goodmicroscope. Most of them have no special common name, and with oneor two exceptions further mention of the mode of distribution of thisfascinating portion of plant life cannot here be made. 

In our botanic garden was planted a patch six feet across of whatis known as Oswego tea, bee balm, or red-flowered bergamot, aninteresting plant with considerable beauty. It grew well for a year, the next year it failed to some extent, and on the third most of theplants died, or nearly died, excepting the spreading portion allaround the margin. This is a fairy ring of another type, and representsa very slow mode of travel. As further illustrations of this topicstudy 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 timewithout transplanting. 

The roots of plants are seldom much observed, because they are outof sight. In soft ground the roots of the common or black locust extendfrom twenty to forty feet in each direction, and almost anywhere alongthese 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 spreadingas though the parent trees were able to move about. A number of kindsof poplars and willows, ailanthus, some of the elms, ashes, sweetpotatoes, milkweeds, Canada thistles, and others behave in a similarmanner. Little bits of Canada-thistle root half an inch long may sendforth buds, and each bud grow to be an independent plant. 

[Illustration: FIG. 1. --Buds and shoots sprouting from roots of thecommon locust. ]

Roots have a peculiarity not usually known. They stretch out and crookabout here and there, penetrating the crevices of the soil whereverthere is the least chance, and the matured portions begin to shorten, reminding one somewhat of an angleworm when one end has been steppedon. By this shortening process the top or crown of a dandelion orplantain is pulled down beneath the surface of the ground. 

4. How nature plants lilies. --Lilies grow from bulbs which areplanted six inches beneath the surface. Do you know how nature plantsthem? A seed starts and becomes a small plant on the surface of theleaf mould or a little beneath; little roots push downward and toright and left; and later, after getting a good hold below withnumerous branchlets, the slender roots shorten and tug away at thetiny bulb above, as much as to say, "Come down a little into motherearth, for cold winter is approaching and there will be danger fromfrost. " The young bulb is drawn down an inch more or less, the slenderroots perish with the growing year, but the bulb is preserved. Theseedling was well planned; for while it had yet tender leaves duringits first year, starch and protoplasm were stored up in the thickenedscales of the bulb. During the second spring some of this food instore is used to send down another set of slender roots with themessage to gather in more water, potash, phosphorus, nitrogen, andother substances to help grow a larger bulb. In late summer and autumnthe new roots contract and pull away at the greater bulb, and downit goes into the ground another inch or so. I have a theory as tohow 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 yearto year till the proper depth is reached for preserving the full-grownbulb. 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 outwardlarge numbers of bulblets that form around a parent bulb of some kindsof 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 reportsthat a certain lawn in Vienna was mown so frequently that tulips couldnot go to seed, but after twenty years, from a very few bulbs plantednear each other, a space twenty paces in diameter was well coveredby tulips. And this is one way tulips travel, slow and sure. 

5. Roots hold plants erect like ropes to a mast. --Did you ever liftvines of cucumbers, squashes, and the like, where they had rootedat the joints, and observe how forlorn they looked after the operation, with leaves tipped over, unable to remain erect? While growing, thestem zigzags or winds about more or less, and thus enables it to holdthe leaves erect; besides, the tendrils catch on to weeds and curlup tight, and the roots at the joints are drawn taut on each sideafter the manner mentioned above, and act like ropes to a mast tohold the stem in its place, and thus help to hold the leaf above erect. 

6. How oaks creep about and multiply. --Oaks come from acorns;everybody knows that. The nuts are produced in abundance, and thoseof the white oak send out pretty good tap roots on the same year theyfall. Some of the nuts roll down the knoll or are carried about bysquirrels or birds, as mentioned elsewhere. Let me tell you one thingthat I discovered the white oaks were doing in the sand of theJack-pine plains of Michigan. In dry weather the dead grass, sticks, and logs are often burned, which kills much or all that is growingabove 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 againand again, and, after repeated burnings, form each a large rough masspopularly 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 wheregrubs abound requires a stout plow and several pairs of horses oroxen. 

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 mainroot perishes, and two roots, with branches a little distance apart, support each a cluster of stems above ground. 

[Illustration: FIG. 2. --Small tree, "grub, " of white oak many timeskilled back; finally dead at the middle and sprouting on the margins. ]

[Illustration: FIG. 3. --Grub, or remains of a white oak, doubtlessat one time much like Fig. 2, but now decayed in the middle, includingits main root; sprouting on the margins, farther and farther out afterthe tops were killed, to the ground. ]

[Illustration: FIG. 4. --Grub, or remains of a white oak, still olderthan the one represented in Fig. 3. A hole appears where the tap roothas rotted away. The right-hand portion is already dividing, and intime, if often killed back, we might find several distinct oaks asdescendants from one acorn. ]

There can be no doubt that young oak trees slowly move in this mannerfrom one place to another. If in fifty years we have two distinctgrubs or branches, three or four feet apart, where the connectingpart has finally died out, I see no reason why in another fifty yearseach one of the two may not again have spread and divided, givingus at least four grubs, or clusters of sprouts, all originally comingfrom 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 thetime she wants. 

[Illustration: FIG. 5. --Part of a grub of white oak, still alive andspreading over the ground, the central portions dying, the marginsalive and spreading. ]

CHAPTER III. PLANTS MULTIPLY BY MEANS OF STEMS. 

7. Two grasses in fierce contention. --In growing a lawn at theMichigan Agricultural College, a little Bermuda grass was scatteredwith June grass, and the struggle has been most interesting. In thespring and for six weeks in autumn, when moisture usually aboundsand 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 theBermuda, which continues to spread, assumes control of the lawn, withbut little of the June grass in sight. Each struggles for possessionand 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 closemat of living green which delights the eye and is pleasant to thefeet that tread upon it. In soft ground, with plenty of room, a bitof quick or quack grass, or Bermuda, will extend in a year three tofive feet or more in one direction. 

[Illustration: FIG. 6. --Rootstock of quick grass which has grownthrough a potato, and in this way may be carried to another fieldor 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 ora little way below. These are not roots at all, but true stems somewhatin 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 strawberriesby runners must be familiar to every observer. In 1894 a studentreported that a wild strawberry plant in the botanic garden hadproduced in that year 1230 plants. Weeds were all kept away, the seasonwas favorable, the soil sandy; but on one side, within a foot anda half, progress was checked by the presence of a large plant ofanother kind. The multiplication of this plant by seeds, in additionto that by runners, would have covered a still greater area of land. Other plants with runners much like the strawberry are: several kindsof crowfoot, barren strawberry, cinquefoil, strawberry geranium, andorange hawkweed. Plants of the star cucumber, one-seeded cucumber, grapes, morning-glories, and others, spread more or less over bushesor over the ground, and are thus enabled to scatter seeds in everydirection. 

[Illustration: FIG. 7. --The runner of a strawberry plant. ]

9. Branches lean over and root in the soil. --A black raspberry growsfast in the ground and has to stay in one spot for life. It has neitherlegs, feet, nor wings, and yet it can travel. The bush takes deeproot and spreads out its branches, which are sometimes ten feet ormore in length; the tips of these branches curve over to the groundsix feet away, and finally take root; from these roots new coloniesare formed, five to twenty in a year from one bush. 

True, the old roots do not get far, and the new plants only get aboutsix feet in one season, but they have made some progress. This israther slow locomotion, you say; but let us look a little farther, remembering that a seed is a little plant packed ready fortransportation. This second mode of spreading will be described ona future page. 

[Illustration: 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. --Sometrees and shrubs among the willows are called snap-willows, becausetheir branches are very brittle; on the least strain from wind, rain, sleet, or snow, the smaller branches snap off near the larger branchesor the main trunk, and fall to the ground. At first thought thisbrittleness of the wood might seem to be a serious defect in thestructure of the tree or shrub, although they seem to produce branchesenough for their own use. 

But the branches which are strewn all around after a storm often takeroot in the low ground where they fall; some of them are carried downstream by the current, and, lodging on the shore below, produce newtrees or bushes. During the winter of 1895 and 1896 a group of sevenwhite willows, near a brook on the campus of the Michigan AgriculturalCollege, was at one time loaded with sleet. There was considerablesnow on the ground, which, of course, was covered with an icy crust. In a little while the sleet melted from the fallen branches strewnabout, and a moderate breeze then drifted the smallest of the twigsin considerable numbers over the icy snow. Some of these were foundthirty rods distant from the parent trees--not down stream in thevalley of the brook, but up the stream. Had not the low ground beencovered with a dense growth of grass, some of these branches mighthave started new trees where the wind had left them. [1]

[Footnote 1: C. D. Lippincott believes that this is a provision ofnature to dispose of the now unnecessary branchlets without leavinga knot. _Plant World_, Vol. I, p. 96. ]

[Illustration: FIG. 9. --Branch of snap-willow rooting at one end. ]

The branches on slow-growing limbs of cottonwood and large-toothedaspen are much enlarged at the nodes, and at these places are brittle, often separating from the tree and breaking up into pieces. Undera small cottonwood were picked up a bushel or more of such limbs, all yet alive. These trees are common on low land, and, likesnap-willows, the severed twigs may find a chance to grow on moistsoil. [2]

[Footnote 2: The brittle branches of salix were noticed by the authorin _Bull. Torr. Bot. Club_, Vol. IX (1883), p. 89. ]

[Illustration: FIG. 10. --Portion of a branch of the cottonwood asit fell from the tree. ]

In a greenhouse a potted plant of _Selaginella emiliana_(?) wasplaced on the bench near the aisle, where it was often brushed bypeople in passing. Small branches, not being firmly attached, werefrequently broken from the main plant and fell upon the moist sand, where they rooted in abundance. 

CHAPTER IV. WATER TRANSPORTATION OF PLANTS. 

11. Some green buds and leaves float on water. --Loosely floating onslow streams of the northern states, in water not the purest, mayoften be found the common bladderwort, _Utricularia vulgaris_, producing in summer a few yellow flowers on each stem, rising fromsix to twelve inches above the water. The lax, leafy branches in thewater are from six inches to a foot long. The leaves, or thread-likebranches, are about half an inch long, more or less, and several timesdivided. 

[Illustration: 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 itsnames. For a long time the bladders were thought to serve merely aslife-preservers; it was supposed that they were constructed to keepthe plant from sinking to the bottom. In reality these bladders helppreserve the plant in another sense, by catching and killing largenumbers of minute animals, on which the plant lives in part. The tipsof the stems at all times of the year are rather compact, made upof young leaves and stems, and in the middle of the summer, as wellas at other times, many may be seen severed from the parent plant, floating in the water, ready to accept the assistance of any favorablecurrent or breeze and start out for homes of their own to found newcolonies. These olive-green tips, or buds, vary much in size, butthe largest are the size of the end of one's little finger. Late inautumn or early winter, when cold threatens, the tender buds contracta little, and, having thus become heavier than water, slowly go to thebottom to spend the winter safely protected in the soft mud. All theplant perishes except these buds. With the lengthening days of springthe melting ice disappears, and genial sunshine gives notice to thedormant buds that it is safe to come out again. The buds begin toexpand, become lighter than water, and are soon seen spreading out atthe surface and producing branches and leaves. Ducks and otherwater-fowl not infrequently carry some of these wet buds sticking totheir feathers or legs. 

In this connection the following plants may be examined from timeto time: _Lemna_, _Wolffia_, _Anacharis_ (_Elodea_), _Myriophyllum_, _Cabomba_, and several species of _Potamogeton_. I have seen theleaves of lake cress, _Nasturtium lacustre_, often spontaneouslyseparate from the stem, possibly carrying at the base the rudimentsof a small bud, which draws on the floating leaf for nourishment andproduces a small plant near its base. These plants, floated andnourished by the mother leaf, may drift down a creek or across a pondand establish new settlements. In a similar manner behave leaves ofthe following, and perhaps others: _Cardamine pratensis_, horse-radish, celandine, some water lilies, and other plants notgrown in wet land. 

[Illustration: FIG. 12. --Floating leaf of lake cress, _Nasturtiumlacustre_, with a young plant growing from the base. ]

Gardeners often propagate certain species by placing leaves on wetsand or mud, when buds spring from the margins of the leaves or fromsome other portion. 

One of the buttercups, _Ranunculus multifidus_, and very likelyothers, spread over the mud by producing runners, much after themanner of a strawberry plant. If, as in case of a freshet, the plantsshould be covered with water, they show their enterprise by takingadvantage 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 theloosestrifes, _Lysimachia stricta_, a plant growing in bogs, besidesreproducing itself by rootstocks and seeds, bears fleshy buds halfan inch long, which separate from the stems and take root in the mudnear the parent plant, or often float to another spot. The buds onthe stems of _Cicuta bulbifera_ develop into small bulbs, whichreadily separate from the plant. They then float on the water andproduce new plants. The tiger lily also produces bulblets, whichscatter about and promptly take root. Every person of goodunderstanding must have heard or read about seeds carried by oceancurrents or transported by lake, pond, creek, or by muddy current, during, and after, a shower of rain; in most of these the wind isalso a prominent factor. Many seeds and fruits, in some cases parts, and even the whole, of plants seem to be purposely designed for thismode of travel, while an innumerable host of others occasionally makeuse of it, although it may seem from their structure and place ofgrowth that they were made especially to be transported by the windor by some animal. As has been seen in examples previously mentioned, one portion of a plant is transported in one way, and another portionby one or two other methods. 

[Illustration: FIG. 13. --Branch of loosestrife bearing tuberbulblets. ]

[Illustration: FIG. 14. --One of the tubers enlarged. ]

13. Seeds and fruits as boats and rafts. --An excellent place in whichto begin investigating this part of the subject is to pay a visitto the flats of a creek or river late in autumn or in the spring, after the water has retired to its narrow channel, and examine pieceafter piece of the rubbish that has been lodged here and there againsta knoll or some willows, a patch of rushes or dead grass. We arestudying the different modes by which plants travel. In the driftwoodmay be found dry fruits of the bladder nut, brown and light, an inchand a half in diameter. See how tough they are; they seem to beperfectly tight, and even if one happens to have a hole punched inits side, there are probably two cells that are still tight, for thereare three in all. Within are a few seeds, hard and smooth. Why arethey so hard? Will it not be difficult for such seeds to get moistenough and soft enough to enable them to germinate? The hard coatsenable 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 afterthe tough pod has decayed and the seeds have sunken to the moist earthamong the sticks and dead leaves, they can have all the time theyneed for the slow decay of their armor. Sooner or later a tiny plantis likely to appear and produce a beautiful bush. Engineers areboasting of their steel ships as safe and not likely to sink, becausethere are several compartments each in itself water-tight. In caseof accident to one or two chambers, the one or two remaining tightwill still float the whole and save the passengers. 

[Illustration: FIG. 15. --Fruit of bladder nut with three tightcells. ]

I wonder if the engineers have not been studying the fruit of thebladder nut? But this is not all. Many of the dry nuts hang on allwinter, or for a part of it, rattling in the wind, as though loathto leave. Some of them are torn loose, and in winter there will bea better chance than at any other time for the wind to do the seedsa favor, especially when there is snow on the ground, for then theywill bound along before the breeze till something interrupts them. 

Here among the rubbish are some shriveled wild grapes also. As weshall 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 areleft there is another mode of travel, not by wings of a bird, butby floating on water. 

[Illustration: FIG. 16. --Shriveled wild grapes overlooked by birds, now ready to float on water, and a clean seed not able to float. ]

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 dogwoodsare eaten for the pulp by birds, but in case any are left they behaveafter the manner of grapes. 

14. Bits of cork around the seeds prevent them fromsinking. --Narrow-leaved dock is a prominent weed, and is especiallyat home on river bottoms and on low land that is flooded once in awhile. 

[Illustration: FIG. 17. --Fruit and adherent calyx of narrow-leaveddock; a cross section and a naked, seed-like fruit (enlarged). ]

Did you ever wonder what could be the object of a round, spongytubercle on the outside of each of these sepals which hold the ripenedseed closely? I did not know their use for a long time, but now thinkI have discovered their meaning. They are not exactly life-preservers, but the next thing to it. The naked, seed-like fruit, the shape ofthe fruit of buckwheat, sinks at once when free from everything else, but with the dry calyx still attached, it floats with the stream. 

15. An air-tight sack buoys up seeds. --Here are several dry fruitsof sedges--plants looking considerably like grasses. There are a goodmany kinds, and most of them grow in wet places. The seed-like fruitof those we examine are surrounded each by a sack which is considerablytoo large for it, as one would be likely to say, but in reality itserves to buoy the denser portion within, much after the plan of thebladder nut. In some instances the sack is rather small, but a corkygrowth below the grain helps to buoy it on water. 

[Illustration: FIG. 18. --Fruit of Asa-Gray sedge with an inflatedsack about it. ]

Sedges that grow on dry land usually have the sack fitted closely, instead of inflated, and the whole mass sinks readily in water. Nowwe see the probable reason why the sack is inflated in some speciesof sedges and not in others. 

[Illustration: FIG. 19. --Fruit of _Carex communis_, an upland sedge, that readily sinks when placed in water; the sack fits closely. ]

Here are some small, seed-like fruits, _achenes_, not likely to berecognized by every one. They belong to the arrowhead, _Sagittaria_, found in shallow ponds or slow streams. They are flattened, and onone edge, or both, and at the apex is a spongy ridge. Very likely, by this time, the reader has surmised that this serves the purposeof a raft to float the small seed within, which would sink at onceif separated from the boat that grew on its margins. In this connectionmay be studied achenes of water plantain, _Alisma_, bur reed, cat-tail flag, arrow grass, burgrass, numerous pondweeds, severalbuttercups, the hop, nettles, wood nettle, false nettle, cinquefoil, avens, ninebark, buttonbush, and in fact a large number and varietyof plants usually found on river bottoms. 

[Illustration: FIG. 20. --Seed-like fruit of arrowhead with corkymargins to float on water. ]

[Illustration: FIG. 21. --Seed-like fruit of bur reed with corkylining ready to float on water, and a naked seed, such as sinkspromptly. ]

One of the lyme grasses, _Elymus Virqinicus_, is a stiff, short grass, growing along streams. Each spikelet with its chaff adheres to twoempty glumes, stout, thick, and spongy, which make a safe double boatfor 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, theyare good floaters. 

[Illustration: FIG. 22. --Grains of lyme grass with two corky emptyglumes attached, which serve as a raft. ]

In the driftwood, which we still have under consideration, are somefruits of maple, beech, oak, tulip tree, locust, and basswood. Maplesare well scattered by the wind, but these seed-like fruits have takento the water, and a few still retain vitality. An acorn, while yetalive, sinks readily, and is not suited for water navigation, unlessby accident it rides on some driftwood. The fruits of the tulip tree, locust, and basswood behave well on the water, as though designedfor the purpose, though we naturally, and with good reason, classthem with plants usually distributed by wind. 

16. Fruit of basswood as a sailboat, and a few others as adapted tothe water. --In spring, when the bracts and fruits of the basswoodare dry and still hanging on the tree, if a quantity of them are shakenoff into the water which overflows the banks of a stream, many ofthese, as they reach the water, will assume a position as follows:The nuts spread right and left and float; the free portion of thebract extends into the water, while the portion adhering to thepeduncle rises obliquely out of the water and serves as a sail todraw along the trailing fruit. After sailing for perhaps fifteenminutes, the whole bract and stem go under water, the nuts floatingthe 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 forsailing through the air, aided by their numerous long, silky hairs. These hairs are no hindrance to moving by water. I discovered onelittle thing in reference to the seed which makes me think the Designerintended it should to some extent be carried by water. The flat seedhas a margin, or hem, which must be an aid to the wind in drivingit about; but this margin is thickened somewhat by a spongy material. 

[Illustration: FIG. 23. --Seed of milkweed with a corky marginenabling it to float; a seed with such margin removed sinks at once. ]

With the margin it floats, without it the seed sinks in fresh water. A few cranberries were found in the driftwood. These containconsiderable air in the middle, near where the seeds are placed, asthough the air was intended to support them on top of water. 

[Illustration: FIG. 24. --Cranberry containing an air space whichhelps it to float. ]

These berries are colored and edible--qualities that attract thebirds. And here we find in several places the bulblets of a wild garlic, _Allium Canadense_, which grows on the river bottom. These bulbletsare produced on top of the stem with the flowers, and float on thewater. The seeds of the white water lilies, and yellow ones also, by special arrangement float about on the water with the current orthe wind. The coffee tree grows rather sparingly along some of thestreams, and on moist land as far north as Clinton County, Michigan. The stout, hard pods are three to four inches long, one and one-quarterto one and one-half inches wide, and one-half inch thick. The veryhard seeds are surrounded with sweet pulp, which most likely madeit an inducement for some of our native animals to devour them andthus transport the undigested seeds to remote localities. The podsoften remain on the trees all winter, and when dry, will float onthe water of overflowed streams without any injury resulting to thehard 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 oflamb's-quarters and amaranths--the smooth and the pricklypigweeds--still standing where they grew in the summer. These arefavorite feeding grounds for several kinds of small birds, especiallywhen snow covers the ground. 

Many of the seeds, while still enclosed in the thin, dry calyx, andthese clustered on short branches, drop to the snow and are carriedoff by the wind. Notwithstanding the provision made for spreadingthe seeds by the aid of birds and the wind, the calyx around eachshiny seed enables it to float also; when freed from the calyx, itdrops at once to the bottom. Many kinds of dry fruits and seeds inone way or another find their way during winter to the surface ofthe ice-covered rivers. When the rivers break up, the seeds arecarried down stream, and perhaps left to grow on dry land after thewater has retired. Most of the commonest plants, the seeds of whichare usually transported by water, are insignificant in appearanceand without common names, or with names that are not well understood. This is one reason for omitting the description of others which areingeniously fitted in a great variety of different ways for travelingby water. 

18. Tumbleweeds. --Incidentally, the foregoing pages contain someaccount of seeds and fruits that are carried by the aid of wind, inconnection with their distribution by other methods; but there aregood reasons for giving other examples of seeds carried by the wind. There is a very common weed found on waste ground and also in fieldsand gardens, which on good soil, with plenty of room and light, growsmuch 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 mostprominent of our tumbleweeds. It does not start in the spring fromseed till the weather becomes pretty warm. The leaves are small andslender, the flowers very small, with no display, and surrounded bylittle rigid, sharp-pointed bracts. When ripe in autumn, the dry, incurved branches are quite stiff; the main stem near the groundeasily 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 freeaccess. 

The mother plant, now dead, toiled busily during the heat of summerand produced thousands of little seeds. The best portion of hersubstance went to produce these seeds, giving each a portion of richfood 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 ofher precious progeny, most of whom will find new places, where theywill stand a chance the next summer to grow into plants. Sometimesthe winds are not severe enough or long enough continued, and theseold skeletons are rolled into ditches, piled so high in great rowsor masses against fences that some are rolled over the rest and passon beyond. Occasionally some lodge in the tops of low trees, and manyare 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 inother directions, to be broken up and scatter seeds along theirpathway. 

During the Middle Ages in southern Egypt and Arabia, and eastward, a small plant, with most of the peculiarities of our tumbleweed justdescribed, was often seen, and was thought to be a great wonder. Itwas 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 thishabit are well known on dry plains in various parts of the world;one of the most prominent in the northern United States is calledthe Russian thistle, which was introduced from Russia with flaxseed. In Dakota, often two, three, or more grow into a community, makingwhen dry and mature a stiff ball two to three feet or more in diameter. 

[Illustration: FIG. 25. --Mature dry plant of Russian thistle as atumbleweed. (One-seventh natural size. )]

One of our peppergrasses, _Lepidium intermedium_, sometimes attainsthe size and shape of a bushel basket; when ripe, it is blown about, sowing seeds wherever it goes. The plants of the evening primrosesometimes 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 beennaturalized from Europe, has developed recently on strong clay landinto a tumbleweed six inches in diameter. The tops of old witch grass, _Panicum capillare_, and hair grass, _Agrostis hyemalis_, becomevery brittle when ripe, and snap from the parent stem and tumble aboutsingly or in masses, scattering seeds by the millions. I have seenpiles of these thin tops larger than a load of hay where they hadblown against a grove of trees, and in some cases many were caughtin the tops of low trees. 

[Illustration: FIG. 26. --The top of old witch grass as a tumbleweed. (Reduced two thirds. )]

Bug seed and buffalo bur are tumbleweeds. In autumn the carefulobserver with an eye to this subject will be rewarded by finding manyother plants that behave more or less as tumbleweeds. Especially isthis the case on prairies. These are annuals, and perish at the closeof the growing season. There are numerous other devices by which seedsand fruit secure transportation by the wind. 

19. Thin, dry pods, twisted and bent, drift on the snow. --The commonlocust tree, _Robinia Pseudacacia_, blossoms and produces largenumbers of thin, flat pods, which remain of a dull color even whenthe seeds are ripe. The pods of the locust may wait and wait, holdingfast for a long time, but nothing comes to eat them. They become dryand slowly split apart, each half of the pod usually carrying everyother seed. Some of the pods with the seeds still attached are tornoff by the wind and fall to the ground sooner or later, accordingto the force of the wind. Each half-pod as it comes off is slightlybent and twisted, and might be considered a "want-advertisement"given to the wind: "Here I am, thin, dry, light and elastic, twistedand bent already; give me a lift to bear these precious seeds up thehill, into the valley, or over the plain. "

[Illustration: FIG. 27. --Two views of a half-pod of common locust, dry, twisted, and bent, ready for a breeze. ]

And the wind is sure to come along, a slight breeze to-day tossingthe half-pod a few feet, leaving it perhaps to be again and againmoved farther forward. The writer has seen these half-podstransported by this means more than a block. But many of the podsstick to the limbs till winter comes. Then a breeze tears off a fewpods and they fall on the snow, which has filled up all the crevicesin the grass and between the dead leaves and rubbish. Each half-pod, freighted with every other seed, is admirably constructed; like anice boat, it has a sail always spread to the breeze. In this way thereis often nothing to hinder some of the seeds from going a mile ortwo in a few minutes, now and then striking some object which jarsoff a seed or two. The seeds are very hard, and no doubt purposelyso, that they may not be eaten by insects or birds; but once in moistsoil, the covering slowly swells and decays, allowing the young plantto escape. Thus the locust seeds are provided with neither legs, wings, fins, nor do they advertise by brilliant hue and sweet pulp; but theytravel in a way of their own, which is literally on the wings of thewind. 

20. Seeds found in melting snowdrifts. --It will interest the studentof nature to collect a variety of seeds and dry fruits, such as canbe found still on the trees and other plants in winter, and try someof them when there is snow on the ground and the wind blows, to seehow they behave. Again, when the first snow banks of the early winterare nearly gone, let him collect and melt a quantity of snow and searchfor seeds. By this means he can see, as he never saw before, how oneneighbor suffers from the carelessness of another. 

21. Nuts of the basswood carried on the snow. --Here are some notesconcerning the distribution of the spherical nuts of basswood. Thesmall clusters of fruit project from a queer bract which remainsattached before and after falling from the tree. 

[Illustration: FIG. 28. --Fruit and bract of basswood well adaptedfor 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 fivenuts about the size of peas usually remain attached till winter, oreven a few till spring. This bract has attracted a good deal ofattention, and for a long time everybody wondered what could be itsuse. We shall see. The cluster of nuts and the bract hang down, dangling about with the least breath of wind, and rattling on thetrees because the enlarged base of the stem has all broken looseexcepting two slender, woody threads, which still hold fast. Thesethreads are of different degrees of strength; some break loose aftera 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 thefruit can be carried depends on the form of the bract, the velocityof the wind, and the smoothness of the surface on which the fruitfalls. When torn from the tree the twist in the bract enables thewind to keep the cluster rapidly whirling around, and by whirlingit is enabled to remain longer suspended in the air and thus increasethe chances for a long journey. In throwing some of these from athird-story window, it was found that a bract with no fruit attachedwould reach the ground sooner than a bract that bore from two to foursolid nuts. The empty or unloaded bracts tumble and slide throughthe 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, thefaster its descent, and the more a bract whirls when the wind blows, the farther it is carried. The bract that is weighted with a loadof fruit acts as a kite held back by a string, and when in this positionthe wind lifts the whole as well as carries it along. Before snowhad fallen in 1896, by repeated moves on a well-mowed lawn, fruitand bracts were carried about two hundred feet, while with snow onthe ground the distance was almost unlimited, excepting where therewere obstructions, such as bushes and fences. When there is a cruston the snow and a good wind, the conditions are almost perfect. Overthe snow the wind drives the bracts, which drag along the branch offruit much as a sail propels a boat. The curving of the edges of thebract 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 directionof 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. Afterwatching these maneuvers, no one could doubt the object of the bentbracts of the basswood, and as these vary much in length and widthand shape on different trees, it would seem that perhaps nature isstill experimenting with a view to finding the most perfect structurefor the purpose. 

About one hundred and thirty paces west of the house in which I livestand two birch trees. One windy winter day I made some fresh tracksin the snow near my house, and within a few minutes the cavities lookedas though some one had sprinkled wheat bran in them, on account ofthe many birch seeds there accumulated. 

Other fruits in winter can be experimented with, such as that of boxelder, black ash, birches, tulip tree, buttonwood, ironwood, bluebeech, and occasionally a maple. 

22. Buttonwood balls. --Nature seems to have no end of devices forsowing 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 ballsgrow on the tops of the highest branches, and hold on into winteror longer. The stems are about two inches long, and soon after drying, through the action of the winds, they become very flexible, eachresembling a cluster of tough strings. The slightest breeze movesthem, and they bob around against each other and the small branchesin an odd sort of way. After so much threshing that they can holdno longer, the little nuts become loosened and begin to drop off afew at a time. Certain birds eat a few and loosen others, which escape. The illustration shows some of these nuts, each supplied with a ringof bristles about the base, which acts as a parachute to permit thewind the easier to carry them for some distance before falling, orto drift them on the surface of the snow or ice. 

[Illustration: FIG. 29. --(a) Lax stem, supporting (b) fruit of thebuttonwood, or sycamore; (c) a single fruit separated, ready for thewind or water. ]

23. Seeds that tempt the wind by spreading their sails. --On low landsin the cool, temperate climate of Europe, Asia, and North America, is a common plant here known as great willow-herb, a kind of fireweed(_Epilobium angustifolium_). There are several kinds of fireweeds. This one grows from three to five feet high, and bears pretty pinkflowers. In mellow soil the slender rootstocks spread extensively, and each year new sprouts spring up all around, six to eight feetdistant. Below each flower ripens a long, slender pod, which splitsopen from the top into four parts, that slowly curve away from acentral column. The apex of each seed is provided with a cluster ofwhite silky hairs nearly half an inch long. 

[Illustration: FIG. 30. --Fruit of willow-herb exposing seeds fordistribution by the wind. ]

The tips of the hairs stick slightly to the inside of the recurvedvalves, some hairs to one valve, and often others to the adjacentvalve, thus spreading them apart with the seed suspended between. Four rows of the seeds are thus held out at one time. Often not overhalf, or even a tenth part, of the seeds are well developed, yet thesilky hairs are present and float away in clusters, thus helping tobuoy those that are heavy. This is a capital scheme, for when thepods are dry and unfurled, they silently indicate to the slightestbreath of air that they are ready for a flight, and it doesn't takemuch to carry them for a long distance. As an active boy delightsto venture again and again over thin ice on a shallow pond in thepasture, half fearing, yet half hoping, that he may become a heroby breaking through and escaping, so likewise many of these seedsand seed-like fruits spread themselves out, as if to tempt the windto come along and attack them. 

The twin fruits of the parsnip and some of its near relatives arelight and thin and split apart, each holding on lightly to the topof a slender stem. In this position they are sure to be torn off sooneror later. Somewhat after the manner of the willow-herb behave thepods and seeds of willows, poplars, milkweeds, Indian hemp, andcotton. 

[Illustration: FIG. 31. --Dry twin fruits of the parsnip held byslender stems ready to be blown away. (Much enlarged. )]

24. Why are some seeds so small?--Do you know why so many kinds ofplants produce very small and light seeds? Would it not be betterif they produced fewer and larger seeds, which would then be strongerand better able to grow under adverse conditions? But a large numberof small seeds cost the plant no more effort than a small number oflarge ones, and the lighter and smaller the seeds and the more thereare of them, the better their chances for distribution, especiallyfor long distances. The minute size of spores of most of the fungiare given as reasons why so many of them are so widely distributed. 

Why is a boy or man of light weight chosen to ride the horse on therace track? That the animal may have less weight to carry and therebyuse his surplus strength in making better time. The less weight theparachute of the seed of the willow-herb has to carry, the greaterthe chances for success in making a long journey. Of the willow-herbit takes one hundred seeds to weigh a milligram, including the hairsattached to them, and it would take thirty thousand to weigh as muchas an ordinary white bean. 

25. Seeds with parachutes. --Many years ago large portions of Huronand Sanilac counties of eastern Michigan were swept by a fire so severethat the timber was all killed. Fifteen years later the woody growthconsisted mostly of willows, poplars, and birches. The seeds of allkinds of willows and poplars are very light, and are produced inimmense quantities. Like those of the great willow-herb, they arebeautifully constructed for making long journeys through the air--afact that explains the frequency of these trees in burned districts. A considerable number of seeds and fruits grow with a parachuteattached at one end, not to prevent injury by falling from the treetop, but to enable the wind to sustain and transport them for a longerdistance. 

26. A study of the dandelion. --In spring the dandelion is almosteverywhere to be found; every one knows it--the child to admire, thegardener to despise. From each cluster of leaves spreading flat inthe grass come forth several hollow stems, short or tall, dependingon the amount of sunshine and shade. Each stem bears, not one flower, but a hundred or more small ones. Around and beneath each yellowcluster are two rows of thin, green, smooth scales (involucre). 

[Illustration: FIG. 32. --Heads of the dandelion in fruit, closed andopen. ]

The short outer row soon curls back, as though for rest or ornament, or for watching the progress of the colony above; but the inner rowhas a very important duty yet to perform in guarding the large familywithin. At night, or in daytime, if the day be wet, the long scalespress like a blanket closely about the flowers, and do not permitthem to come out; but when the sun is bright, it shrinks the outerside of these scales, which then curl apart, leaving the yellowflowers ready for bees to visit or boys to admire and study. Forseveral days the flowers of a head blossom in succession, each nightto be snugly wrapped by the scales, and the next day to be again leftopen, if the weather be fine. After each flower in turn has beenallowed to see the light, and after all have been crawled over bybee and wasp to distribute the yellow pollen that seeds may be produced, there is nothing else to do but patiently wait for a week or two whilereceiving food from the mother plant to perfect each little fruitand seed. During all this period of maturing, day and night, rainor shine, the scales hold the cluster closely; the stem bends overto one side, and the rain and dew is kept from entering. After a while, on some bright morning, the dandelion stalk is seen standing erectagain, and is probably surrounded by many others in a similar position. The dry air shrinks the outside of the scales, and they turn downward;the circle of feathers at the top of the slender support attachedto the seed-like fruit below spreads out, and the community, whichnow looks like a white ball of down, is ready for a breeze. The featherytop is now ready to act as a parachute, and invites the wind to catchup the whole and float it away. If there is no breeze, the moist airof night closes the outer scales; each of the feathery tips closes, and all are secure till the next bright day. 

Of a like nature are fruits of thistles, fireweed, prickly lettuce, sow thistles, scabiosa, valerian, cat-tail flag, cotton grass, someanemones, smoke tree, virgin's bower, and some of the grasses. 

27. How the lily sows its seeds. --Ripened pods of lilies usually standstraight up on a stiff, elastic stem; beginning at the top, each oneslowly splits into three parts, which gradually separate from eachother. Why do they not burst open all of a sudden, like pea pods, and shoot the seeds all about and have the job done with? Or why doesnot the pod burst open at the lower end first, instead of the upper?

[Illustration: FIG. 33. --At the left a dry fruit of a lily openingto permit seeds to dry and the wind to enter; to the right, a fruitlater in the season. Two views of a flat seed. ]

Observe that the three opening cells are lashed together loosely witha latticework. No slight breeze can dislodge the seeds, but just seehow they behave in a good gale! The elastic stems are swayed backand forth against each other, and some of the upper seeds are tossedout by the wind that passes through the lattice, and at such timesare often carried to some distance. The seeds at the top having escaped, the dry pods split down farther and still farther and open still wider, till the bottom is reached. As the seeds are not all carried awaythe first or even the second time, and as succeeding breezes may comefrom different directions, it is thus possible for the lily to scatterits seeds in all directions. 

The seeds of the lily are flat, very thin, and rather light, notdesigned to be shot out like bullets, but to be carried a little wayby the wind; the pods are erect, and open at the top, that the seedsneed not escape when there is no wind or unless some animal givesthe stem a strong shake. The latticework was made for a purpose, andthe gradual opening of the pods prevents the supply from all goingin one direction or in one day, for a better day may arrive. The studentwill look for and compare the following: Iris, figwort, wild yam, catalpa, trumpet-creeper, centauria, mulleins, foxglove, beardtongue, and many other fruits. 

28. Large pods with small seeds to escape from small holes. --The largeripe pod of the poppy stands erect on a stiff stem, with a numberof small openings near the top. The seeds are nearly spherical, andescape, a few at a time, when the stem is shaken by the wind or someanimal, thus holding a reserve for a change of conditions. Here isan illustration of ripe pods of a bellflower, _Campanula turbinata_, nodding instead of erect. 

[Illustration: FIG. 34. --Ripe pod of poppy on an erect, stiff stem, ready for wind or animal to shake out a few seeds at the top. ]

[Illustration: FIG. 35. --Ripe pods of bellflower bent over; the holesopening when dry to allow seeds to be shaken out. ]

The small holes are still uppermost, but to be uppermost in this caseit is necessary for them to be at the base of the pod. 

29. Seeds kept dry by an umbrella growing over them. --When mature, the apple of Peru, _Nicandra_, keeps every dry bursting fruit coveredwith a hood, umbrella, or shed, so that seeds may be kept continuallydry and may be spread with every shake by the wind, or by an animal, in rainy weather as well as in dry. 

In the words of Dr. Gray, "The fruit is a globular dry berry, enclosedby a five-parted, bladdery inflated calyx. " The margins of the lobesof the calyx curl upwards and outwards as the berry hangs with theapex downward. 

[Illustration: FIG. 36. --Mature fruit of apple of Peru covered byan enlarged calyx. ]

[Illustration: FIG. 37. --The same with the calyx removed. ]

[Illustration: FIG. 38. --The same as Fig. 37, except that it is olderand somewhat changed. ]

The berry is as large as one's thumb, and when ripe, bursts openirregularly on the upper side as it hangs up under the calyx. As thecovering of the pod opens more and more, a few seeds at a time maybe rattled out by wind or animal. The numerous large and light fruits, with calyx surrounding them, are each supported on a nodding stem, stiff and elastic, which gives the wind a good chance to sway themabout. Water does not seem to get into the berries even when theyare torn open, for when it is poured over the branches it rolls offthe calyx roof as freely as from a duck's back. The fruits of_Physalis_ are apparently kept dry in a manner similar to the appleof Peru, although when first mature they are soft and juicy, considerably like a ripe tomato. 

30. Shot off by wind or animal. --The calyx of sage, bergamot, andmost other mints, remains dry and stiff, as a cup to hold one to fourlittle round nutlets as they ripen. The figure shows two of thesein section, as they are attached to the main stem of the plant, orone of its branches. Observe the direction taken by the upper andby the lower points of the calyx. When dry, the plant behaves somewhatas follows: when the wind jostles the branches against each other, or when an animal of some kind hits the plant, this movement causesmany of these cups to get caught; but the elastic stem comes suddenlyback to its place, and in so doing flips a nutlet or more from itsmouth one to six feet, somewhat as a boy would flip a pea with apea-shooter. In our garden, July 2, when plants of sage, _Salviainterrupta_, were ripening their fruit, we found it difficult tocollect any seeds, but seedlings were observed in abundance on everyside of the plant, some to the distance of six feet. Plants dispersingseeds in this manner have been called catapult fruits. Examineripening fruits of blue curls, pennyroyal, germander, balm, horehound, dittany, hyssop, basil, marjoram, thyme, savory, catmint, skullcap, self-heal, dragon's head, motherwort, and various dryfruits of several chickweeds. 

[Illustration: FIG. 39. --Ripe calyx of sage, first as pushed down;second as let loose throwing nutlets. ]

31. Seed-like fruits moved about by twisting awns. --Most of thegrains of grasses are invested with glumes, or chaff, and aconsiderable per cent of the chaff has awns, some of which are welldeveloped and some poorly developed. The distribution of such grassesdepends on several agents--wind, water, and animals. The chaff andawns of all are hygroscopic; that is, are changed by differencescaused by variation of moisture in the air. Sweet vernal grass, talloat grass, holy grass, redtop, animated or wild oats, blue-joint, and porcupine grass are among them. When mature, the grain and glumesdrop off, or are pushed off, and go to the ground. When moist, theseawns untwist and straighten out, but when dry they coil up again;with each change they seem to crawl about on the ground and work downto low places or get into all sorts of cracks and crevices, wherethe first rain is likely to cover them more or less with earth, afterwhich they are ready for growth. 

32. Grains that bore into sheep or dogs or the sand. --Porcupine grass, _Stipa spartea_, grows in dry soil in the northern states, but moreparticularly on the dry prairies of the central portion of the UnitedStates. This grass, when ripe, has a very bad reputation amongranchmen for the annoyance the bearded grain causes them. The grainsare blown into the stubble among grasses with the bearded point down, sticking into the soil. The first rain or heavy dew straightens outthe awns, which are twisted again as they dry. The bearded point worksa little farther with each change, and after twisting and untwistinga number of times it gets down three or four inches into the sand, often to moisture, where the awns decay and the grain germinates. Here is an admirable scheme for moving about and for boring into theground. But this is not all. The grains are quick to catch fast toclothing, as people move among the plants, and they are admirablyfitted for attaching themselves to dogs and sheep, which they annoyvery much. These animals transport the grains for long distances. The twisting and untwisting of the awns enable the grain to borethrough the fleeces, and even to penetrate the skins and make woundswhich sometimes cause the death of the animal. Examine also seedsof pin clover, Alfilerilla, which is becoming abundant in many partsof the world. 

[Illustration: FIG. 40. --Ripe fruit of pin clover, or Alfilerilla, ready to twist into fleeces of sheep or into loose soil. ]

33. Winged fruits and seeds fall with a whirl. --The large fruit ofthe silver maple falls in summer. As these trees are most abundantalong the margins of streams, the fruit often drops into the waterand is carried down stream to some sand drift or into the mud, wheremore sand is likely to cover them. Thus sown and planted and watered, they soon grow and new trees spring up. But in many instances a strongbreeze, sometimes a whirlwind, has been seen to carry these maturefruits from the tree to a distance of thirty rods. 

[Illustration: FIG. 41. --Single fruit of silver maple. ]

A thin sheet of paper descends more slowly than the same materialput in the form of a ball. On the same principle, many seeds and fruitsare flattened, apparently for a purpose; not that they may be easilyshot through the air by some elastic force, not to increase theirchances for attachment to animals, but to enable the wind to sustainthem the longer and carry them farther. Some seeds and dry fruitsare said to have wings, with the general understanding that they areby this means better fitted to be sustained in air. We shall findthat all or nearly all flattened seeds and dry fruits, also wingedseeds and fruits, are one-sided, unbalanced, and more or lesstwisted; consequently, in falling to the ground they whirl about, and are thus kept much longer in the air than they would be if shapedmore like a winged arrow. Even the wings on the fruit of some of theashes are twisted, though many of them are flat. Experiments withthese things are sure to interest inquisitive children, or even olderpersons, when once started right; they are likely to prove asinteresting as flying kites, skating, fishing, or coasting on thehillside. Try experiments with seeds of catalpa, trumpet-creeper, wild yam, pine, spruce, arbor vitæ, and fruits of maple, box elder, birch, hop tree, blue beech, ailanthus, ash, tulip tree, --in fact, anything of this nature you can find, whether the name is familiaror not. No two of them will behave in all respects alike. 

[Illustration: FIG. 42. Winged seed of pine. Want of symmetry causesit to whirl about while falling. ]

34. Plants which preserve a portion of their seeds for anemergency. --Many a great general or business man has learned byexperience and observation that it is usually unwise to exhaust allresources in one effort. If possible, he always plans to havesomething in reserve for an emergency--a loophole for escape fromdifficulty. We have seen in many instances that plants are endowedwith the same trait. This is well illustrated by the way in whichthe jack-pine, _Pinus_ [_Banksiana_] _divaricata_, holds in reservea portion of its seeds, to be used in case the parent trees are killedby fire. In 1888 I made a study of this tree as it lives on the sandyplains of Michigan. The tree is often killed by fire, and never sproutsfrom the stump, as do oaks, willows, cherries, and most other trees. The jack-pine grows readily and rapidly from seed dropped on the sand, and begins to bear cones and seeds in abundance while it is yet onlya few years old, perhaps as young as five years in some instances. The cones open slowly to liberate their seeds, some of them only aftermonths or even years, and in some cases they never open at all. Ihave seen cones containing good seeds that had been nearly grown overby the tree. Dry weather, the dryer and hotter the better, causesmany of these stubborn old cones to open their scales and allow theseeds to escape. What can be the advantage in cones of this nature?Let us see. A brisk fire passes over the ground at irregular intervals, usually of from one to ten years; it licks up all dry leaves and sticks, and kills the pine trees and all else above ground. The soil and thetrunks of trees are blackened, and by lack of reflection the heatof the sun is rendered more intense; besides, the heat of the fireacts slowly on the unburned cones as they are left on the dead trees. By the time the quick hot fire has passed over, the cones have slowlyopened and begun scattering seeds on the vacant and newly burnedground, at a time when there is the best possible chance for themto grow. I picked a few unopened cones which, according to my judgment, were from two to four years old. They were placed under glass in adark sheet-iron dish and exposed to the sun. The extra heat causedthe cones to open; many seeds were obtained and sown, and in fivedays they began to come up, 95 per cent germinating. From the sametree I selected at the same time older cones, which I believe to befrom four to six years old at least. From these, 225 seeds were sown, 191 of which germinated--about 85 per cent. 

[Illustration: FIG. 43. --Cone of jack-pine closely covering itsseeds, often for several years. ]

[Illustration: FIG. 44. --Cone of jack-pine as opened by heat, sowingseeds. ]

CHAPTER VI. PLANTS THAT SHOOT OFF THEIR SPORES OR SEEDS. 

By numerous devices a large number of the lower plants send off theirripe spores with considerable force. Some call them sling fruits. One in particular, _Pilobolus cristallinus_, found about dampstables, I have observed to shoot black masses of spores to a spoton a wall six feet above the ground, with enough force to have carriedthem not less than twelve feet. When ripe and dry, the spores of mostferns are shot from the parent plant by a motion forcible enough notonly to burst the _sporangium_, the vessel that contains the spores, but also to turn it inside out. 

[Illustration: FIG. 45. --Spores of _Pilobolus_ before and whileshooting its spores. ]

35. Dry pods twist as they split open and throw the seeds. --In December, while absent from home, I collected for future study some pods ofthe Chinese wistaria, and left them on my desk in the library forthe night. The house was heated by a hot-air furnace. In the morningthe pods were in great confusion; most of them had split and curledup, and the seeds were scattered all about the room. As usual thelittle daughter, an only child, was accused of spoiling my specimens, but she showed her innocence. A little investigation and a fewexperiments with some pods not yet opened explained the whole mattersatisfactorily. The stout pods grow and ripen in a highly strainedcondition, with a strong tendency to burst spirally, the twohalf-pods being ready to coil and spring in opposite directions; whenthe valves can no longer hold together, they snap with a sharp noiseand sling the heavy seeds, giving them a good send-off into the world. As a pair of birds build a nest, hatch eggs, rear their young, andthen send them forth to seek their fortunes, so for months the motherplant had labored, had produced and matured seeds, which at last itscattered broadcast. Goethe, Kerner von Marilaun, each independently, and very likely others, had an experience with ripe pods brought toa warm room very similar to my own. In many cases the ripe and dryingfruits are "touched off" by wind jostling the branches or by animalspassing among them; in the latter case there is a chance that a portionof the discharges will be lodged somewhere on the animal and be carriedalong with it. 

36. A seed case that tears itself from its moorings. --The perennialphlox in cultivation distributes its seeds in the following manner:when ripe, the calyx becomes dry and paper-like, and spreads out inthe form of a saucer. The thick-walled dry pistil opens from the topinto three pieces with a snap, spreading open so far against the calyxthat it is torn from the brittle attachment; away go the seeds, mingledwith the fragments of the pistil, no longer of any use. 

[Illustration: FIG. 46. --A dry pod of wild bean bursting spirallyto throw the seeds. ]

[Illustration: FIG. 47. --Fruit of violet partially dried and splitinto three pieces, each piece pinching the seeds so closely thatsooner or later all are thrown out. ]

Fruits that sling their seeds are to be found in every neighborhood, and are first-class objects for the curious person to see and handle. Very fortunate is the girl or boy who is never fully satisfied withwhat he reads and sees pictured, but has a strong desire to learnhow plants are made and how they behave. A considerable number ofseed pods have been illustrated with notes in recent schoolbooks. Here are some of them: peas and vetches, and some kinds of beans, violets, balsams, wood sorrel, geranium, castor bean, some of themustards and cresses and their cousins, Alfilerilla, richweed, _Pilea_, witch-hazel, and others. Each of those will well repay study, especially the fruit and seeds of oxalis. The witch-hazel bears ahard, woody, nut-like fruit, as large as a hazelnut; when ripe, theapex gaps open more and more, the sides pressing harder against eachsmooth seed, till finally it is shot, sometimes for a distance ofthirty feet. The girl who has shot an apple seed or lemon seed withpressure of thumb and finger across a small room, can understand theforce needed to shoot a seed but little heavier than that of the appletwo or three times that distance. 

[Illustration: FIG. 48. --Dry fruit of witch-hazel shooting seeds. ]

CHAPTER VII. PLANTS THAT ARE CARRIED BY ANIMALS. 

With the frosts of autumn ripe acorns, beechnuts, bitternuts, butternuts, chestnuts, hickory nuts, hazelnuts, and walnuts aresevered from the parent bush or tree and fall to the ground amongthe leaves. 

37. Squirrels leave nuts in queer places and plant some of them. --Evenbefore the arrival of frosts many of these are dropped by the aidof squirrels, gray and red, which cut the stems with their teeth. The leaves, with the help of the shifting winds, gently cover thefruit, or some portions of it, and make the best kind of protectionfrom dry air and severe cold; and they come just in the nick of time. Dame Nature is generous. She produces an abundance; enough to seedthe earth and enough to feed the squirrels, birds, and some otheranimals. The squirrels eat many nuts, but I have seen them carry aportion for some distance in several directions, and plant one ortwo or three in a place, covering them well with soil. It may be thethought of the squirrel--I cannot read his thoughts--to return atsome future time of need, as he often does. But in some cases he forgetsthe locality, or does not return because he has stored up more thanhe needs; or in some cases the squirrels leave that locality or arekilled; in any such case the planted nuts are not disturbed. At allevents, some of the nuts--one now and then is all that is needed--areallowed to remain where planted. In this way the squirrel is a benefitto the trees and pays for the nuts he eats. He has not lived in vain, for he is a tree planter and believes in arboriculture. His arborday comes in autumn, and he needs no message from the governor tostimulate him to work. 

After some red squirrels had been given black walnuts, a member ofmy family saw them hide the nuts in all conceivable places, and insome instances place them above a cluster of small branches of a treefor support where three or more twigs spread from nearly the sameplace. Here the nuts, one in a place, were left till perhaps shakento the ground by a severe wind or by some other cause. In one winter, without hunting for them, six to ten places were found in oneneighborhood of Michigan, where something had placed a single walnutor acorn in the forks of small branches. In some cases a severe windcould have dislodged the nut. 

[Illustration: FIG. 49. --A black walnut as left by a red squirrelon a small oak tree. ]

On February 18, 1897, I found a single black walnut held by smallbranches of a red oak. 

The oak was an inch and a half in diameter, and the nut was aboutsix feet from the ground. The nearest bearing tree was fully threehundred long steps distant. We can imagine that, through fright orother causes, a squirrel might be suddenly interrupted while carryingnuts, and might then drop them to the ground, where later a tree wouldbe started. 

38. Birds scatter nuts. --The work of birds in scattering seeds andfruits has long been recognized. [3]

[Footnote 3: In the fall of 1897, Prof. C. F. Wheeler saw a blue jayfly from a white oak tree with an acorn in its mouth. The bird wentto the ground four or five rods distant and crowded the acorn intothe soil as far as it could, covering the spot with a few leaves. A member of my family saw a blue jay leave half of a black walnutin the forks of several small branches. ]

Some friends of mine collected a quantity of hazelnuts, while yetthe green husks enclosed the nuts, and placed them near the houseto dry. At once they were discovered by a blue jay, which picked outa nut at a time, flew away, held the nut between its toes, crackedit from the small end, and ate the contents. In this operation a numberof nuts slipped away and were lost. But it seems that all were noteaten, for the next season half a dozen or more hazel shoots cameup, and to-day a new patch of hazel bushes is growing in the yard. Doubtless many acorns are carried from place to place and droppedin an aimless way by woodpeckers, blue jays, and crows; also beechnutsby these birds, and by nuthatches, and by pigeons, before the latterbecame nearly extinct. Woodpeckers and blue jays place beechnuts andsmall acorns in the crevices of bark on standing trees. If left therevery long, the nuts will become too dry to grow, but in the act oftransporting them some of the nuts may be accidentally dropped invarious places. 

39. Do birds digest all they eat?--To determine whether seeds wouldlose their vitality in passing through the digestive organs of birds, Kerner von Marilaun fed seeds of two hundred and fifty differentspecies of plants to each of the following: blackbird, song thrush, robin, jackdaw, raven, nutcracker, goldfinch, titmouse, bullfinch, crossbill, pigeon, fowl, turkey, duck, and a few others; also tomarmot, horse, ox, and pig, making five hundred and twenty separateexperiments. As to the marmot, horse, ox, and pig, almost all thefruits and seeds were destroyed. From the ox grew a very few seedsof millet, and from the horse one or two lentils and a few oats; fromthe pig a species of dogwood, privet, mallow, radish, and commonlocust. Under ordinary conditions, no seed was found to germinateafter passing through the turkey, hen, pigeon, crossbill, bullfinch, goldfinch, nutcracker, titmouse, and the duck. Ravens and jackdawspassed without injury seeds of stone fruits and others with very hardcoats. Of seeds that passed through the blackbird 75 per centgerminated, 85 per cent in the case of the thrush, 80 per cent inthe case of the robin. [4]

[Footnote 4: It should be noted that the blackbird here mentionedis not the same as either of our blackbirds, but a thrush much likeour robin; that the robin mentioned is a ground warbler nearly relatedto our bluebird. It should also be noted that jackdaws, ravens, thrushes, and probably many others eject thousands of seeds by themouth for one which passes through the intestines. ]

40. Color, odor, and pleasant taste of fruits are advertisements. --Insummer, buds are formed on bushes of black raspberry, blossoms appear, and these are followed by small, green, and bitter berries, whichhardly anything cares to eat. They grow slowly, become soft and pulpy, and finally good to eat. How is bird or boy or girl to know wherethey are and when they are fit to eat? The plant has enterprise andhas displayed two want advertisements by painting the berries firstdark red, and then dark purple, when they are good to eat. But isthe plant made expressly to produce berries, just to feed birds andchildren? If that be all, why are seeds formed in the berries in suchlarge numbers? No! They produce berries that contain seeds, and fromthese seeds are to grow more bushes. Then why should not the berriesalways remain bitter or hard, so that nothing would touch them? Ifwe may say so, the plant produces sweet and showy berries on purposeto be eaten, that the seeds may be carried away. What becomes of theseeds? Each one is enclosed in a hard, tough covering, which protectsit from destruction in the stomachs of many birds and some otheranimals. The seeds are well distributed by the animals that eat theberries. The brilliant colors of ripe berries say to bird and child:"Here we are; eat us, for we are good. " The sweet pulp pays the birdsfor distributing the seeds, else they would not be so distributed. The seeds are as well provided for locomotion as the ticks, the mites, and the spiders, and when ready to go, the berries flaunt their colorsto attract attention. You see, then, that although the old parentbush cannot change its place, young bushes grow from the tips of thebranches, and seedlings spring up at long distances from their oldhomes. 

[Illustration: FIG. 50. --Raspberry, ripened, picked, and ready tobe eaten. ]

Sparrows, finches, and similar birds in the winter eat and destroyseeds of grasses and weeds, while the same birds in summer and autumneat bushels of blueberries, huckleberries, elderberries, raspberries, strawberries, and similar fruits, and distribute theirunharmed seeds over thousands of acres, which otherwise might neversupport a growth of these species. 

The downy woodpecker, among other things, devours berries of threekinds of dogwood, Virginia creeper, service berry, strawberry, pokeberry, poison ivy, poison sumac, stag-horn sumac, and blue beech. 

The hairy woodpecker devours many of the above fruits, as well asthose of spicebush, sour gum, cherries, grapes, blackberries. Theflicker devours most of the fruits listed for the two woodpeckersnamed above, also hackberry, black alder, green brier, bayberries. A number of other woodpeckers possess habits much the same as thethree above named. The cedar bird devours many species of hard-seededfruits. 

The various shades of red appear to good advantage among green leaves. As illustrations of such, we have the wintergreen, partridge berry, bush cranberry, bearberry, service berry, currant, holly, strawberry, red-berried elder, winter berry, honeysuckle, and many more. Wherethe leaves are liable to become red in autumn the berries are oftenblue. Of such, notice wild grapes, blueberries, and berries ofsassafras, though the flowering dogwood has red leaves as well asred berries. 

There is a reason for prickles on rosebushes. When ripe, rosehipsare usually red or yellow, and thus attract birds which are fond ofthe fleshy portion outside; but the seed-like nuts are too hard anddry to suit their taste, and are rejected and sown in the vicinity, where the ripened hips are picked in pieces and eaten. Mice and redsquirrels are also fond of the seed-like nutlets of roses, but seldomsecure them from the bushes. Why, do you ask? Because the prickleswere most likely placed on the rosebushes to prevent this very thing, and not to annoy the lover of flowers, or to prevent her from cuttingwhat she needs. 

41. The meddlesome crow lends a hand. --"One of the most industriousand persistent seed-transporting agencies I know of is thatubiquitous, energetic, rollicking, meddlesome busybody, the crow. I have seen crows gather by hundreds and have a regular powwow, amass convention, where they seemed to discuss measures and appointofficers. At length they get through, and as they start to fly awaymany, if not all, will drop something. I have found these to be acorns, walnuts, hickory nuts, buckeyes, sycamore balls, sticks, eggshells, pebbles, etc. As a crow leaves an oak he will pluck an acorn, whichhe may carry five miles and light on a beech tree where somethingelse will attract his attention, when he will drop the acorn and maybepluck a pod of beechnuts and fly away somewhere else. "--_Prof. W. B. Barrows_. 

The number of seeds distributed by crows is enormous, and consistsof many species, including poison ivy and poison sumac, wild cherry, dogwood, red cedar, sour gum, and Virginia creeper. The hard, undigested seeds are mostly expelled from the mouth in pellets, shownin the illustration, and germinate more promptly than those untouchedby birds. 

[Illustration: FIG. 51. --Two views of a pellet of seeds and rubbishfrom a crow. From bulletin No. 6, United States Department ofAgriculture, Division of Ornithology and Mammology. ]

Bears are very fond of berries, and will scatter the seeds of serviceberries, elder berries, chokecherries, raspberries, andblackberries. 

42. Ants distribute some kinds of seeds. --Ants are numerous, strong, skillful, and in suitable weather are always very busy. Their habitshave been investigated, and it has been found that in some respectsthey are genuine farmers on a small scale. They have their slaves(not hired help); they feed their plant lice, remove them from placeto place, and otherwise care for them, because the lice constituteone of the chief sources of their supply of sweet. They build roadsand houses, and enjoy society after their fashion. They have use forcertain kinds of seeds, portions or all of which they eat at onceor carry to their homes. A number of persons in different countriesand at different times have seen ants carrying seeds. Some youngstudent of botany may have noticed along one side of the glossy seedsof the bloodroot a delicate, fleshy ridge, and wondered what couldbe its use. The answer can now be given with a good degree of confidence. The ants either eat this fleshy ridge at once, or, as more frequentlyhappens, carry such seeds to their homes. The smooth seeds they donot eat, but cast them out of their nests after using the part theylike; after being rejected the seed may stand a chance to germinate. The seeds cannot be carried so well unless this ridge, _caruncle_, be present. Other seeds of this nature are those of wild ginger, celandine, cyclamen, violet, periwinkle, some euphorbias, bellwort, trillium, prickly poppy, dutchman's breeches, squirrel-corn, several species of Corydalis, Seneca snakeroot, and other speciesof milkworts. 

[Illustration: FIG. 52. --Seed of bloodroot with caruncle or crest, which serves as a handle for ants to hold on to. Ant ready to takethe seed. ]

[Illustration: FIG. 53. --A view of a seed of euphorbia with a softbunch at one end, a handle for ants. ]

In his work on _Vegetable Mold and Earthworms_, p. 113, Darwin statesthat earthworms are in the habit of lining their holes, using seedsamong other things, and that these sometimes grow. In this way theworms aid in spreading plants. 

43. Cattle carry away living plants and seeds. --In Arizona, wherecacti abound, Professor Toumey finds that many of them are brokenin pieces by cattle, which eat a portion, while other portions oftenadhere to the legs or noses and are carried from place to place. Thesefragments are usually capable of growing. 

The unicorn plant, _Martynia proboscidia_, common in thesouthwestern portion of the United States, is sometimes seen incultivation. When ripe, the fruit is hard, carrying two stout beakswith recurved tips. Experiments show it to be admirably adapted tocatch on to the feet of sheep, goats, and cattle, or hold to the fleecesof the two former. 

[Illustration: FIG. 54. --Dry fruit of the unicorn plant adapted tocatching on to the feet of large animals or the wool of sheep. ]

44. Water-fowl and muskrats carry seeds in mud. --Seeds and fruitsof aquatic and bog plants that are floating, or in the mud of shallowwater, are often carried by ducks, herons, swallows, muskrats, andother frequenters of such places, on their feet, beaks, or feathers, as they hastily leave one place for another. In this way seeds ofwater plantain, sedges, grasses, rushes, docks, arrowhead, pondweeds, duckweed, cat-tail flag, bur reed, bladderwort, water crowfoot, andmany others are transported from one pond, lake, or stream, to another. In some cases enough of a living plant may be detached and carriedaway to keep on growing. Darwin found on the feet of some birds sixand three-quarter ounces of mud, in which were five hundred andthirty-seven seeds that germinated. Mud may be carried on the feetof land animals as well as on aquatic animals, not only from pondsand bogs, but from the fields where seeds may have accumulated inthe earth or washed down the slopes. 

45. Why some seeds are sticky. --Some seeds and fruits are sticky;in some instances the mucilaginous substance is normally moist enoughto adhere to anything that touches it, while in other cases it requiresto be wetted before it will adhere. The seeds of flax, plantain, peppergrass, basil, sage, dracocephalum, groundsel, drop-seed grass, and many others less familiar, possess this peculiarity. The berriesof some plants, when fully ripe, burst very easily when touched, andsome of the seeds are then likely to adhere to animals and be carriedaway. Some berries of several plants belonging to the nightshadefamily have this peculiarity, as well as some of the cucurbits. Whenthe outer covering of seeds of water lilies, arums, and others arebroken, the gummy secretion is very likely to adhere to the feathers, or fur, or feet of animals. A number of fruits, and even the upperfruit-bearing branches, have sticky glands with which to catch onto any passing object. Among these are some kinds of sedges, chickweeds, and catchflies. 

The sticky substance on seeds and fruits not unfrequently servesanother good turn besides enabling them to adhere to animals. Theslime holds them to the spot where they are to grow, or it enablessome to float or to sink in water, according to the amount of themucilage. 

46. Three devices of Virginia knotweed. --A perennial plant, four tofive feet high, grows on low land, usually in the shade. It is_Polygonum Virginicum_, and so far without a common name, unlessVirginia knotweed be satisfactory. It is a near relative of knot grassand smartweed and Prince's feather. The small flowers are borne ona long, elastic, and rather stiff stem, and each flower stalk hasa joint just at the base. As this fruit matures, the joint becomesvery easy to separate. It dries with a tension, so that, if touched, the fruit goes with a snap and a bound for several feet. The shakingproduced by the wind jostling several against each other issufficient to send off a number of ripe fruits in every direction. Like many other plants we have seen, this has more than one way ofscattering seeds, and often more than two ways. Observe the slender, stiff beak, terminating in two recurved points. Let a person or someanimal pass into a patch of these plants, and at once numerous fruitscatch on wherever there is a chance, and some are shot upon or intothe fleeces of animals, there to find free transportation foruncertain distances. Should there be a freshet, some of these fruitswill float; or, in case of shallow currents after a rain, some ofthem are washed away from the parent plant. Any inquisitive personcannot fail to be pleased if he experiment with the plant when thefruit is ripe. 

[Illustration: FIG. 55. --Fruit of Virginia knotweed ready to shootoff when shaken, or to let go of stem and catch on to passing animal. ]

47. Hooks rendered harmless till time of need. --There are a numberof rather weedy-looking herbs, common to woods or low land, knownas Avens, _Geum_. They are closely allied to cinquefoil, and allbelong to the rose family. The slender stiles above the seed-likeovaries of some species of Avens are described as not jointed, butstraight and feathery, well adapted, as we might suppose, to bescattered by the aid of wind; while others are spoken of as having, when young, stiles jointed and bent near the middle. In ripening, the lower part of the stile becomes much longer and stouter. Whena whole bunch of pistils has drawn all the nourishment possible, orall that is needed, from the plant mother, the upper part of eachstile drops off, leaving a sharp, stiff hook at the end. At this timeeach pistil loosens from the torus and can be easily removed, especially if some animal touch the hooks. To help in holding fastto animals, there are a number of slender hairs farther down the stile, which are liable to become more or less entangled in the animal'shair, fur, wool, or feathers. Even in the small number of plants herenoticed, we have seen that scarcely any two of them agree in thedetails of their devices for securing transportation of seeds. I knowof nothing else like the Geum we are now considering. When young andgreen, the tip of each hook is securely protected by a knob or bunch, with a little arm extending above, which effectually prevents thehook from catching on to anything; but, when the fruit is ripe, theprojecting knob with its little attachment disappears. The figuresmake further description unnecessary. To keep the plow from cuttinginto the ground while going to or from the field, the farmer oftenplaces a wooden block, or "shoe, " over the point and below the plow. Sometimes we have known persons to place knobs of brass or wood onthe tips of the sharp horns of some of their most active or viciouscattle, to prevent them from hooking their associates or the personshaving them in charge. Nature furnishes the points of the young fruitsof some species of Avens with knobs, or shoes, for another purpose, to benefit the plants without reference to the likes or dislikes ofanimals. 

[Illustration: FIG. 56. --The pistil of Avens in three stages of itsgrowth. ]

48. Diversity of devices in the rose family for seed sowing. --Allbotanists now recognize plants as belonging to separate families, the plants of each family having many points of structure in common. Among these families of higher plants, over two hundred in number, is one known as the rose family. Notwithstanding their closerelationship, the modes of seed dispersion are varied. The seeds ofplums and cherries and hawthorns are surrounded by a hard pit, orstone, which protects the seeds, while animals eat the fleshy portionof the fruit. When ripe, raspberries leave the dry receptacle andlook like miniature thimbles, while the blackberry is fleshythroughout. The dry, seed-like fruits of the strawberry are carriedby birds that relish the red, fleshy, juicy apex of the flower stalk. 

Each little fruit of some kinds of Avens has a hook at the apex, whilein Agrimony many hooks grow on the outside of the calyx and aid incarrying the two or three seeds within. Plants of some other familiesillustrate the great diversity of modes of dispersion as well as theroses. 

49. Grouse, fox, and dog carry burs. --To the feathers of a ruffedgrouse killed in the molting stage, early in September, were attachedfifty or more nutlets of _Echinospermum Virginicum_ Lehm. 

A student tells of a tame fox kept near his home, on the tail of whichwere large numbers of sand burs, and a smaller number on his legsand feet. Another student has seen dogs so annoyed by these burs ontheir feet that they gave up all attempts to walk. 

Many wild animals unwillingly carry about such fruits, and after awhile most of them remove what they can with claws, hoof, or teeth. Many of these plants have no familiar common names, but who has notheard of some of these? enchanter's nightshade, bedstraw, wildliquorice, hound's tongue, beggar-ticks, beggar's lice, stick-tights, pitchforks, tick-trefoil, bush clover, motherwort, sand bur, burdock, cocklebur, sanicle, Avens, Agrimony, carrot, horse nettle, buffalo bur, Russian thistle. Besides these, a verylarge number of small seeds and fruits are rubbed off and carriedaway by animals. Some of these stick by means of the pappus, as, forinstance, the dandelion, thistle, prickly lettuce; others by meansof hairs on the seed, such as those of the willow-herb and milkweedsand willows; or by hairs on the fruit, as virgin's bower, anemone, cotton grass, and cat-tail flag. These last named are apparentlydesigned to be wafted by the wind, but they are ever ready to improveany other opportunity offered, whether it be by water or by clingingto passing animals. 

[Illustration: FIG. 57. --Whole ripe fruit of the common carrot. ]

[Illustration: FIG. 58. --Nutlet of stickseed, _Echinospermum_. ]

[Illustration: FIG. 59. --Fruit of pitchforks, _Bidens_, with twobarbed points. ]

[Illustration: FIG. 60. --A fruit of tick-trefoil, _Desmodium_, anda few of the grappling hooks enlarged. ]

[Illustration: FIG. 61. --A head of the fruits of burdock. ]

[Illustration: FIG. 62. --Fruit of cocklebur. ]

50. Seeds enough and to spare. --In producing seeds nature is generous, often lavish. Most seeds are eaten by animals, or fall in places wherethey cannot germinate and produce plants, or fall in such numbersthat most of them in growing are crowded and starved to death. A verysmall proportion fall on good ground, and succeed in becomingfruiting plants. A large plant of purslane produces one million twohundred and fifty thousand seeds; a patch of daisy fleabane, threethousand seeds to each square inch of space covered by a plant. Thegenuine student will not be satisfied till he has selected severaldifferent kinds of plants and counted, or estimated, the number ofseeds produced by each, or the number of seeds furnished to the areacovered by one or by several plants. 

CHAPTER VIII. MAN DISPERSES SEEDS AND PLANTS. 

In describing the various means by which plants are dispersed, peopleare very likely not to mention the aid supplied by man, or to speakof his efforts as artificial or unnatural, forgetting for the timethat man so far appears to be the crown of earthly existence, andthat his works are a necessary part of a complete world. 

51. Burs stick to clothing. --Late in summer or in autumn, who is therewho has not returned from a walk along the river or from a tramp throughthickets or the open woods, to find large numbers of half a dozenkinds of seed-like fruits sticking to his clothes? When ripe, thesefruits usually separate from the parent plant very easily, by a jointor brittle place well provided for in the early part of the season. In pursuing your way you rub off a portion of these fruits, and atthe end of the journey, or before, you sit down in some comfortablespot and deliberately pick off the unwelcome stick-tights. At suchtimes you have been the means of transporting seeds, and you haveleft them scattered about ready to grow. If you ever were so fortunateas to live on a farm, you must have seen your father or his hiredhelp carefully look about the field or the wood lot and remove allthe bur-bearing plants that could be found before turning in his flockof sheep or the colts and cattle; for if this were not done, he knowsthat hair and mane will surely be disfigured, and that the wool willbe rendered unsalable. In removing the weeds he defeated the plansof Nature in her devices for sowing seeds. 

The agency of man in the distribution of plants exceeds in importancethat of all other means combined. He buys and sells seeds and plants, and sends them to all parts of the habitable globe. He exterminatesmany plants in large areas, and substitutes in large measure thoseof his choice. Mixed with seeds of grasses, clovers, or grains, heintroduces many weeds and sows them to grow with his crops. 

[Illustration: FIG. 63. --Seed of cockle (enlarged). ]

[Illustration: FIG. 64. --Grain of wheat (enlarged), scarcely largerthan a seed of cockle. ]

L. H. Dewey, in the Yearbook of the Department of Agriculture forthe year 1896, p. 276, says: "Cockle seeds are normally somewhatsmaller than wheat grains. In some parts of the northwest, where wheatfor sowing has been cleaned year after year by steam threshers, allthe cockle seeds except the largest ones have been removed, and thesehave been sown until a large-seeded strain has been bred which isvery difficult to separate from the wheat. " For illustration, someyears ago I purchased of a dealer in Michigan a small quantity ofwhat was being sold on the market as seed of red clover; this specimencontained 40 per cent of seeds of rib-grass or narrow-leavedplantain. 

[Illustration: FIG. 65. --Two seeds of narrow-leaved plantain suchas are becoming common in clover seed. The lower one and the one atthe left are seeds of red clover. ]

Man introduces some seeds of weeds with unground feed stuff. Heintroduces some with barnyard manure drawn from town. He gets somein the packing of nursery stock, crockery, baled hay and straw. Forexample, in 1895, baled hay from Kansas or that vicinity examinedat the Missouri Agricultural College was found to contain fifteenspecies of weeds. Others from the west were examined in Michigan andfound to contain much foul stuff. Some are carried from farm to farmby wagons, sleighs, or threshing machines; or they are spread by plows, cultivators, and harrows. A few are introduced to grow for ornamentor food, and afterwards spread as weeds. A number have been shippedto distant lands in the earth of ballast, which is often unloadedand reloaded at wharves where freight is changed. They are carriedalong the highway, strung along the towpath of canals, or are carriedin the trucks or in the cars of railroads. They are imported andexported around the world in fleeces of wool. They float downirrigating ditches from farm to farm, and with the water are welldistributed. 

52. Man takes plants westward, though a few migrate eastward. --Sofar as man's agency is concerned, the direction for plant migrationis generally westward, in the course taken by himself. In case oftwo hundred kinds of weeds named by the United States Department ofAgriculture, one hundred and eight species are of foreign origin. Three notable samples of weeds in the United States have gone fromthe west to the east, carried in seeds of grasses or clovers. Theseare _Rudbeckia hirta_, _Artemisia biennis_, _Plantago aristata_. Tothese Mr. Dewey adds buffalo bur, _Solanum rostratum_, squirreltail, _Hordeum jubatum_, false ragweed or marsh elder, _Iva xanthifolia_, _Franseria hookeriana_, alfalfa dodder, _Cuscuta epithymum_. 

Above I have barely mentioned a few of the methods by which man isan unwilling agent in distributing plants. Large volumes could befilled with statements of man's more or less carefully plannedattempts to transport seeds and living plants from one part of theworld to another. 

CHAPTER IX. SOME REASONS FOR PLANT MIGRATION. 

53. Plants are not charitable beings. --Man uses to his advantage alarge number of plants, but there appears to be no evidence that theschemes for their dispersion were designed for anything except tobenefit the plants themselves. The elegant foliage and beautifulflowers, the great diversity of attractive seeds and fruits, allpoint to plants as strictly selfish beings, if I may so use the term;and not to plants as works of charity, to be devoured by animalswithout any compensation. By fertilizing flowers, by distributingplants, and by other helpful acts, animals pay for at least a portionof the damage they do. 

By an almost infinite number of devices, we have seen that seeds andfruits flee from the parental spot on the wings of the wind, floaton currents of ocean, lake, and river. They are shot by bursting podsand capsules in every direction. With hooks, barbs, and glands theycling to the covering of animals. Allured by brilliant colors, birdsand other animals seek and devour the fruits of many plants, the seedsof which are preserved from harm by a solid armor; these seeds arethen sown broadcast over the land, ready to start new colonies. Nutsare often carried by squirrels for long distances, and there securelyburied, a few in a place. By a slow process, which, however, coversa considerable space, in a few years many plants send forth roots, rootstalks, stolons, and runners, and thus increase theirpossessions or find new homes. 

54. Plants migrate to improve their condition. --The various devicesby which plants are shifted from place to place are not merely toextend and multiply the species, and reach a fertile soil, but toenable them to flee from the great number of their own kind, and fromtheir enemies among animals and parasitic plants. The adventurersamong plants often meet with the best success, not because the seedsare larger, or stronger, or better, but because they find, for a time, more congenial surroundings. We must not overlook the fact, so wellestablished, that one of the greatest points to be gained by plantmigration is to enable different stocks of a species to be crossfertilized, and thereby improved in vigor and productiveness. 

55. Fruit grown in a new country is often fair. --Every horticulturistknows that apples grown in a new country, that is suited to them, are healthy and fair; but, sooner or later, the scab, and codlingmoth, and bitter rot, and bark louse arrive, each to begin itsparticular mode of attack. Peach trees in new places, remote fromothers, are often easily grown and free from dangers; but soon willarrive the yellows, borers, leaf curl, rot, and other enemies. Fora few years plums may be grown, in certain new localities, withoutdanger from curculio, or rot, or shot-hole fungus. It has long beenknown that the nicest way to grow a few cabbages, radishes, squashes, cucumbers, or potatoes is to plant a few here and there in good soil, at considerable distances from where any have heretofore been grown. For a time enemies are not likely to find them. I have often noticedthat, while pear-blight decimated or swept large portions of a pearorchard, a few isolated trees, scattered about the neighborhood, usually remain healthy. The virgin soil of the Dakotas produced, ata trifling cost, healthy, clean wheat, but it was not long beforethe Russian thistle, false flax, and other pests followed, to contesttheir rights to the soil. 

As animals starve out, in certain seasons when food is scarce, ormore likely migrate to regions which can afford food, so plants desertworn-out land and seek fresh fields. As animals retreat to secludedand isolated spots to escape their enemies, so, likewise, many plantsaccomplish the same thing by sending out scouts in all directionsto find the best places; these scouts, it is needless to say, areseeds, and when they have found a good place, they occupy it, withoutwaiting for further instructions. 

56. Much remains to be discovered. --"In this, as in other branchesof science, we have made a beginning. We have learned just enoughto perceive how little we know. Our great masters in natural historyhave immortalized themselves by their discoveries, but they have notexhausted the field; and if seeds and fruits cannot vie with flowersin the brilliance and color with which they decorate our gardens andour fields, still they surely rival them--it would be impossible toexcel them--in the almost infinite variety of the problems theypresent to us, the ingenuity, the interest, and the charm of thebeautiful contrivances which they offer for our study and ouradmiration. "[5]

[Footnote 5: _Flowers, Fruits, and Leaves_, by Sir John Lubbock, p. 96. ]

Frequent rotations seem to be the rule for many plants, when leftto themselves in a state of nature. Confining to a permanent spotinvites parasites and other enemies, and a depleted soil, whilehealth and vigor are secured by frequent migrations. The more we studyin detail the methods of plant dispersion, the more we shall cometo agree with a statement made by Darwin concerning the devices forsecuring cross-fertilization of flowers, that they "transcend, inan incomparable degree, the contrivances and adaptations which themost fertile imagination of the most imaginative man could suggestwith unlimited time at his disposal. "[6]

[Footnote 6: _Fertilization of Orchids_, p. 351. ]

Let no reader think that the topics here taken up are treatedexhaustively, for if he will go over any part of this work and verifyany observation or experiment, he will be sure to find something new, and very likely something different from what is here stated. 

BIBLIOGRAPHY. 

Means of Plant Dispersion. By E. J. HILL. _Am. Nat. _ Vol. Xvii, pp. 811, 1028. 1883. 

Why Certain Kinds of Timber Prevail in Certain Localities. By JOHNT. CAMPBELL. _Am. Nat. _ Vol. Xix, p. 337. 1885. 

Report of the U. S. Commissioner of Agriculture for 1888. Articleon the "Food of Crows. " By W. B. BARROWS. P. 498. 

Report of the U. S. Secretary of Agriculture for 1890. Article on"Seed Planting by Birds. " By W. B. BARROWS. P. 280. 

Report of the U. S. Secretary of Agriculture for 1893. Article on"Food Habits of the Kingbird, or Bee Martin. " By W. B. BARROWS. P. 233. 

Bulletin No. 6, U. S. Department of Agriculture. Division ofOrnithology and Mammology. "The Common Crow of the United States. "By W. B. BARROWS and E. A. SCHWARZ. 1895. 

Bulletin No. 7, U. S. Department of Agriculture. Division ofOrnithology and Mammology. "Food of Woodpeckers. " By F. E. L. BEAL. 

Causes of Forest Rotation. By JOHN T. CAMPBELL. _Am. Nat. _ Vol. Xx, p. 521. 1886. 

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The Natural History of Plants. By KERNER and OLIVER. Henry Holt &Co. , New York. 1895. 

Flowers, Fruits, and Leaves. By SIR JOHN LUBBOCK. Macmillan & Co. , New York. 

Origin of Cultivated Plants. By ALPHONSE DE CANDOLLE. D. Appleton& Co. , New York. 

Distribution of Weed Seeds by Winter Winds. By H. L. BOLLEY. BulletinNo. 17. Fargo, North Dakota. 

Weeds of California. By E. W. HILGARD. Report of the ExperimentStation, pp. 238-266. 1890. 

Migration of Weeds. By L. H. DEWEY. Yearbook of the U. S. Departmentof Agriculture, pp. 263-286. 1896. Washington, D. C. 

Squirrels Carrying Nuts. _Nature_. Vol. Xv, p. 117. Macmillan & Co. , New York. 

Natural History of Plants. By KERNER and OLIVER. Distribution ofSpecies. Vol. Ii, pp. 790-885. Henry Holt & Co. , New York. 1895.