



Produced by Ron Swanson





SEED DISPERSAL

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




GINN & COMPANY
BOSTON . NEW YORK . CHICAGO . LONDON




COPYRIGHT, 1898
BY WILLIAM J. BEAL

ALL RIGHTS RESERVED
36.11




The Athenaeum Press
GINN & COMPANY . PROPRIETORS . BOSTON . U.S.A.




PREFACE.


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

A brief list of contributions to the subject is given; but, with very
few exceptions, the statements here made, unless otherwise mentioned
in the text, are the results of observations by the author.

I am under obligations for suggestions by my colleague, Prof. W. B.
Barrows; my assistant, Prof. C. F. Wheeler; and a former instructor
of botany, L. H. Dewey, now of the United States Department of
Agriculture. B. O. Longyear, instructor in botany, with very few
exceptions, has made the drawings.

W. J. BEAL.
AGRICULTURAL COLLEGE, MICHIGAN.




CONTENTS.


CHAPTER I.--HOW ANIMALS GET ABOUT.
                                                               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  . . . . . . . . . . 14
10. 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  . . . . . . . . . 18
12. Fleshy buds drop off and sprout in the mud . . . . . . . . . 20
13. Seeds and fruits as boats and rafts  . . . . . . . . . . . . 22
14. Bits of cork around the seeds prevent them from sinking  . . 24
15. An air-tight sack buoys up seeds . . . . . . . . . . . . . . 25
16. 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 . . . . . . . . . . . . . . . . . . . 30
18. Tumbleweeds  . . . . . . . . . . . . . . . . . . . . . . . . 31
19. Thin, dry pods, twisted and bent, drift on the snow  . . . . 35
20. Seeds found in melting snowdrifts  . . . . . . . . . . . . . 36
21. Nuts of the basswood carried on the snow . . . . . . . . . . 37
22. Buttonwood balls . . . . . . . . . . . . . . . . . . . . . . 39
23. Seeds that tempt the wind by spreading their sails . . . . . 40
24. Why are some seeds so small? . . . . . . . . . . . . . . . . 42
25. Seeds with parachutes  . . . . . . . . . . . . . . . . . . . 43
26. A study of the dandelion . . . . . . . . . . . . . . . . . . 44
27. How the lily sows its seeds  . . . . . . . . . . . . . . . . 46
28. Large pods with small seeds to escape from small holes . . . 47
29. Seeds kept dry by an umbrella growing over them  . . . . . . 48
30. Shot off by wind or animal . . . . . . . . . . . . . . . . . 50
31. Seed-like fruits moved about by twisting awns  . . . . . . . 51
32. Grains that bore into sheep or dogs or the sand  . . . . . . 51
33. Winged fruits and seeds fall with a whirl  . . . . . . . . . 52
34. 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  . . . 57
36. 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  61
38. Birds scatter nuts . . . . . . . . . . . . . . . . . . . . . 63
39. Do birds digest all they eat?  . . . . . . . . . . . . . . . 64
40. Color, odor, and pleasant taste of fruits are
       advertisements  . . . . . . . . . . . . . . . . . . . . . 65
41. The meddlesome crow lends a hand . . . . . . . . . . . . . . 68
42. Ants distribute some kinds of seeds  . . . . . . . . . . . . 69
43. Cattle carry away living plants and seeds  . . . . . . . . . 70
44. Water-fowl and muskrats carry seeds in mud . . . . . . . . . 71
45. Why some seeds are sticky  . . . . . . . . . . . . . . . . . 72
46. Three devices of Virginia knotweed . . . . . . . . . . . . . 73
47. Hooks rendered harmless till time of need  . . . . . . . . . 74
48. Diversity of devices in the rose family for seed sowing  . . 76
49. Grouse, fox, and dog carry burs  . . . . . . . . . . . . . . 76
50. Seeds enough and to spare  . . . . . . . . . . . . . . . . . 78


CHAPTER VIII.--MAN DISPERSES SEEDS AND PLANTS.

51. Burs stick to clothing . . . . . . . . . . . . . . . . . . . 80
52. Man takes plants westward, though a few migrate eastward . . 83


CHAPTER IX.--SOME REASONS FOR PLANT MIGRATION.

53. Plants are not charitable beings . . . . . . . . . . . . . . 84
54. Plants migrate to improve their condition  . . . . . . . . . 85
55. Fruit grown in a new country is often fair . . . . . . . . . 85
56. 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 danger
threatens, the rabbit bounds away in long jumps, seeking protection
in a hollow tree, a log, or a hole in the ground. When food becomes
scarce, squirrels quickly shift to new regions. <DW53>s, bears, skunks,
and porcupines move from one neighborhood to another. When the
thickets disappear and hunters abound, wild turkeys and partridges
retreat on foot or by wing. When the leaves fall and the cold winds
blow, wild geese leave the lakes in secluded northern homes, and with
their families, reared during the summer, go south to spend the winter.
Turtles swim from pond to pond or crawl from the water to the sand
bank, where they lay and cover their eggs. Fishes swim up or down
the creek with changing seasons, or seek deep or shallow water as
their needs require. Beetles and butterflies, when young, crawl about
for food and shelter, and when older use their wings in going long
distances.

These examples only serve to recall to mind what every boy or girl
knows and has known ever since he can remember--that most animals
move about whenever they want to, or whenever other animals will let
them.

2. Some animals catch rides in one way or another.--Some small animals,
like lice, ticks, and tiny spiders, walk slowly and only for short
distances. If, because of scarcity of food, they are suddenly seized
with the desire to move for a long distance, what are they to do?
On such occasions ticks and lice watch quietly the first opportunity,
catch on to the feet of birds or flying insects or other animals which
may happen to come their way, and, like a boy catching on to a farmer's
sleigh, ride till they get far enough, then jump off or let go, to
explore the surrounding country and see whether it is fit to live
in. If for some reason a spider grows dissatisfied and wants to leave
the home spot, she climbs to the top of some object and spins out
a fine, long web; this floats in the air, and after a while becomes
so long and light that the wind will bear the thread and the spinner
for a considerable distance, no one knows how far. These facts about
lice and spiders show how wingless insects can go long distances
without wings of their own.

How is it with plants? The woods, fields, marshes, roadsides ever
abound with interesting objects provided with strange devices
waiting to be studied by inquisitive girls and boys in and out of
school, and this finding out of nature's puzzles is one of the deepest
pleasures of life.

How quickly a mould attacks and creeps or spreads through a basin
of berries every one knows. The mould is as much a plant as the bush
that produced the berries; it comes from a small spore, which takes
the place of a bud or sprout or seed. The decay of a tree begins where
a limb or root has been injured, and whether the timber is living
or dead, this decay results from the growth of some one or more low
forms of plant life which enter the timber in certain places and slowly
or quickly penetrate and affect other portions more or less remote.




CHAPTER II.
PLANTS SPREAD BY MEANS OF ROOTS.


3. Fairy rings.--Several low forms of plant life, such as _Marasmius
oreades_, _Spathularia flavida_, and some of the puffballs, start
in isolated spots in the grass of a lawn or pasture, and spread each
year from a few inches to a foot or more in every direction, usually
in the form of a circle; at the end of fifteen years some of these
circles acquire a diameter of fifteen to twenty feet or more. These
are known as fairy rings. Before science dispelled the illusion they
were believed to have been the work of witches, elves, or evil spirits,
from which arose the name.

Several kinds of lichens and mosses and the like, growing on the barks
of trees, fence boards, and low ground, spread slowly in the manner
of fairy rings.

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

It is well known that many of the lower species of plants are more
widely distributed over the earth than most of the higher plants.
Every cloud from a ripe puffball consists of thousands of spores
started on the wings of the wind for an unknown journey. Their habits
are not past finding out, but to examine them a person needs a good
microscope. Most of them have no special common name, and with one
or two exceptions further mention of the mode of distribution of this
fascinating portion of plant life cannot here be made.

In our botanic garden was planted a patch six feet across of what
is known as Oswego tea, bee balm, or red-flowered bergamot, an
interesting plant with considerable beauty. It grew well for a year,
the next year it failed to some extent, and on the third most of the
plants died, or nearly died, excepting the spreading portion all
around the margin. This is a fairy ring of another type, and represents
a very slow mode of travel. As further illustrations of this topic
study common yarrow, betony, several mints, common iris, loosestrife,
coreopsis, gill-over-the-ground, several wild sunflowers,
horehound, and many other perennials that have grown for a long time
without transplanting.

The roots of plants are seldom much observed, because they are out
of sight. In soft ground the roots of the common or black locust extend
from twenty to forty feet in each direction, and almost anywhere along
these roots buds may appear, and a shoot spring up and become a tree.

This peculiarity is worth as much to locusts in the matter of spreading
as though the parent trees were able to move about. A number of kinds
of poplars and willows, ailanthus, some of the elms, ashes, sweet
potatoes, milkweeds, Canada thistles, and others behave in a similar
manner. Little bits of Canada-thistle root half an inch long may send
forth buds, and each bud grow to be an independent plant.

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

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

4. How nature plants lilies.--Lilies grow from bulbs which are
planted six inches beneath the surface. Do you know how nature plants
them? A seed starts and becomes a small plant on the surface of the
leaf mould or a little beneath; little roots push downward and to
right and left; and later, after getting a good hold below with
numerous branchlets, the slender roots shorten and tug away at the
tiny bulb above, as much as to say, "Come down a little into mother
earth, for cold winter is approaching and there will be danger from
frost." The young bulb is drawn down an inch more or less, the slender
roots perish with the growing year, but the bulb is preserved. The
seedling was well planned; for while it had yet tender leaves during
its first year, starch and protoplasm were stored up in the thickened
scales of the bulb. During the second spring some of this food in
store is used to send down another set of slender roots with the
message to gather in more water, potash, phosphorus, nitrogen, and
other substances to help grow a larger bulb. In late summer and autumn
the new roots contract and pull away at the greater bulb, and down
it goes into the ground another inch or so. I have a theory as to
how it finally comes to be drawn down just deep enough and no more,
but I will not venture to give it. This process is repeated from year
to year till the proper depth is reached for preserving the full-grown
bulb. And this is the way nature plants bulbs.

In a similar manner young slender roots well anchored in the soil,
at or near the close of the growing season, pull downward and outward
large numbers of bulblets that form around a parent bulb of some kinds
of leeks, tulips, star-of-bethlehem, globe hyacinth, and monkshood.
The pull of the roots is much greater to one side than downward,
because most of the longest roots extend sidewise. Marilaun reports
that a certain lawn in Vienna was mown so frequently that tulips could
not go to seed, but after twenty years, from a very few bulbs planted
near each other, a space twenty paces in diameter was well covered
by tulips. And this is one way tulips travel, slow and sure.

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

6. How oaks creep about and multiply.--Oaks come from acorns;
everybody knows that. The nuts are produced in abundance, and those
of the white oak send out pretty good tap roots on the same year they
fall. Some of the nuts roll down the knoll or are carried about by
squirrels or birds, as mentioned elsewhere. Let me tell you one thing
that I discovered the white oaks were doing in the sand of the
Jack-pine plains of Michigan. In dry weather the dead grass, sticks,
and logs are often burned, which kills much or all that is growing
above ground. In this way little maples, ashes, witch-hazels, willows,
huckleberries, blackberries, sweet ferns, service berries, aspens,
oaks, and others are often killed back, but afterward sprout up again
and again, and, after repeated burnings, form each a large rough mass
popularly known as a _grub_. The grubs of the oak are well known;
the large ones weighing from 75 to 100 pounds each. To plow land where
grubs abound requires a stout plow and several pairs of horses or
oxen.

A small white oak, after it has been many times killed to the ground,
dies in the middle and sprouts at the margins, and finally the main
root perishes, and two roots, with branches a little distance apart,
support each a cluster of stems above ground.

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

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

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

There can be no doubt that young oak trees slowly move in this manner
from one place to another. If in fifty years we have two distinct
grubs or branches, three or four feet apart, where the connecting
part has finally died out, I see no reason why in another fifty years
each one of the two may not again have spread and divided, giving
us at least four grubs, or clusters of sprouts, all originally coming
from one acorn; and so the matter might go on. This is slow traveling,
I admit, but there is nothing to hinder nature from taking all the
time she wants.

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




CHAPTER III.
PLANTS MULTIPLY BY MEANS OF STEMS.


7. Two grasses in fierce contention.--In growing a lawn at the
Michigan Agricultural College, a little Bermuda grass was scattered
with June grass, and the struggle has been most interesting. In the
spring and for six weeks in autumn, when moisture usually abounds
and the weather is cool, June grass thrives and little else is seen.
In the dry, hot weeks of July and August, June grass rests and the
Bermuda, which continues to spread, assumes control of the lawn, with
but little of the June grass in sight. Each struggles for possession
and does the best it can, and to some extent one supplements the other,
with the result that at all times from spring to fall there is a close
mat of living green which delights the eye and is pleasant to the
feet that tread upon it. In soft ground, with plenty of room, a bit
of quick or quack grass, or Bermuda, will extend in a year three to
five feet or more in one direction.

[Illustration: FIG. 6.--Rootstock of quick grass which has grown
through a potato, and in this way may be carried to another field
or another farm.]

June grass, quick grass, Bermuda grass, redtop, and white clover,
wherever opportunity offers, spread by means of jointed stems,
creeping and rooting at every joint on the surface of the ground or
a little way below. These are not roots at all, but true stems somewhat
in disguise. Here may also be mentioned, as having similar habit,
artichokes, peppermint, spearmint, barberry, Indian hemp, bindweed,
toadflax, matrimony vine, bugle-weed, ostrich fern, eagle fern,
sensitive fern, coltsfoot, St. John'swort, sorrel, great willow-herb,
and many more.

8. Runners establish new colonies.--The spreading of strawberries
by runners must be familiar to every observer. In 1894 a student
reported that a wild strawberry plant in the botanic garden had
produced in that year 1230 plants. Weeds were all kept away, the season
was favorable, the soil sandy; but on one side, within a foot and
a half, progress was checked by the presence of a large plant of
another kind. The multiplication of this plant by seeds, in addition
to that by runners, would have covered a still greater area of land.
Other plants with runners much like the strawberry are: several kinds
of crowfoot, barren strawberry, cinquefoil, strawberry geranium, and
orange hawkweed. Plants of the star cucumber, one-seeded cucumber,
grapes, morning-glories, and others, spread more or less over bushes
or over the ground, and are thus enabled to scatter seeds in every
direction.

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

9. Branches lean over and root in the soil.--A black raspberry grows
fast in the ground and has to stay in one spot for life. It has neither
legs, feet, nor wings, and yet it can travel. The bush takes deep
root and spreads out its branches, which are sometimes ten feet or
more in length; the tips of these branches curve over to the ground
six feet away, and finally take root; from these roots new colonies
are formed, five to twenty in a year from one bush.

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

[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.--Some
trees and shrubs among the willows are called snap-willows, because
their branches are very brittle; on the least strain from wind, rain,
sleet, or snow, the smaller branches snap off near the larger branches
or the main trunk, and fall to the ground. At first thought this
brittleness of the wood might seem to be a serious defect in the
structure of the tree or shrub, although they seem to produce branches
enough for their own use.

But the branches which are strewn all around after a storm often take
root in the low ground where they fall; some of them are carried down
stream by the current, and, lodging on the shore below, produce new
trees or bushes. During the winter of 1895 and 1896 a group of seven
white willows, near a brook on the campus of the Michigan Agricultural
College, was at one time loaded with sleet. There was considerable
snow on the ground, which, of course, was covered with an icy crust.
In a little while the sleet melted from the fallen branches strewn
about, and a moderate breeze then drifted the smallest of the twigs
in considerable numbers over the icy snow. Some of these were found
thirty rods distant from the parent trees--not down stream in the
valley of the brook, but up the stream. Had not the low ground been
covered with a dense growth of grass, some of these branches might
have started new trees where the wind had left them.[1]

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

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

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

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

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

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




CHAPTER IV.
WATER TRANSPORTATION OF PLANTS.


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

[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 its
names. For a long time the bladders were thought to serve merely as
life-preservers; it was supposed that they were constructed to keep
the plant from sinking to the bottom. In reality these bladders help
preserve the plant in another sense, by catching and killing large
numbers of minute animals, on which the plant lives in part. The tips
of the stems at all times of the year are rather compact, made up
of young leaves and stems, and in the middle of the summer, as well
as at other times, many may be seen severed from the parent plant,
floating in the water, ready to accept the assistance of any favorable
current or breeze and start out for homes of their own to found new
colonies. These olive-green tips, or buds, vary much in size, but
the largest are the size of the end of one's little finger. Late in
autumn or early winter, when cold threatens, the tender buds contract
a little, and, having thus become heavier than water, slowly go to the
bottom to spend the winter safely protected in the soft mud. All the
plant perishes except these buds. With the lengthening days of spring
the melting ice disappears, and genial sunshine gives notice to the
dormant buds that it is safe to come out again. The buds begin to
expand, become lighter than water, and are soon seen spreading out at
the surface and producing branches and leaves. Ducks and other
water-fowl not infrequently carry some of these wet buds sticking to
their feathers or legs.

In this connection the following plants may be examined from time
to time: _Lemna_, _Wolffia_, _Anacharis_ (_Elodea_), _Myriophyllum_,
_Cabomba_, and several species of _Potamogeton_. I have seen the
leaves of lake cress, _Nasturtium lacustre_, often spontaneously
separate from the stem, possibly carrying at the base the rudiments
of a small bud, which draws on the floating leaf for nourishment and
produces a small plant near its base. These plants, floated and
nourished by the mother leaf, may drift down a creek or across a pond
and establish new settlements. In a similar manner behave leaves of
the following, and perhaps others: _Cardamine pratensis_,
horse-radish, celandine, some water lilies, and other plants not
grown in wet land.

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

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

One of the buttercups, _Ranunculus multifidus_, and very likely
others, spread over the mud by producing runners, much after the
manner of a strawberry plant. If, as in case of a freshet, the plants
should be covered with water, they show their enterprise by taking
advantage of the "tide"; some of the runners are quickly severed,
and are then at liberty to go as they please.

12. Fleshy buds drop off and sprout in the mud.--One of the
loosestrifes, _Lysimachia stricta_, a plant growing in bogs, besides
reproducing itself by rootstocks and seeds, bears fleshy buds half
an inch long, which separate from the stems and take root in the mud
near the parent plant, or often float to another spot. The buds on
the stems of _Cicuta bulbifera_ develop into small bulbs, which
readily separate from the plant. They then float on the water and
produce new plants. The tiger lily also produces bulblets, which
scatter about and promptly take root. Every person of good
understanding must have heard or read about seeds carried by ocean
currents or transported by lake, pond, creek, or by muddy current,
during, and after, a shower of rain; in most of these the wind is
also a prominent factor. Many seeds and fruits, in some cases parts,
and even the whole, of plants seem to be purposely designed for this
mode of travel, while an innumerable host of others occasionally make
use of it, although it may seem from their structure and place of
growth that they were made especially to be transported by the wind
or by some animal. As has been seen in examples previously mentioned,
one portion of a plant is transported in one way, and another portion
by one or two other methods.

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

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

13. Seeds and fruits as boats and rafts.--An excellent place in which
to begin investigating this part of the subject is to pay a visit
to the flats of a creek or river late in autumn or in the spring,
after the water has retired to its narrow channel, and examine piece
after piece of the rubbish that has been lodged here and there against
a knoll or some willows, a patch of rushes or dead grass. We are
studying the different modes by which plants travel. In the driftwood
may be found dry fruits of the bladder nut, brown and light, an inch
and a half in diameter. See how tough they are; they seem to be
perfectly tight, and even if one happens to have a hole punched in
its side, there are probably two cells that are still tight, for there
are three in all. Within are a few seeds, hard and smooth. Why are
they so hard? Will it not be difficult for such seeds to get moist
enough and soft enough to enable them to germinate? The hard coats
enable the seeds to remain uninjured for a long time in the water,
in case one or two cells of the papery pods are broken open; and after
the tough pod has decayed and the seeds have sunken to the moist earth
among the sticks and dead leaves, they can have all the time they
need for the slow decay of their armor. Sooner or later a tiny plant
is likely to appear and produce a beautiful bush. Engineers are
boasting of their steel ships as safe and not likely to sink, because
there are several compartments each in itself water-tight. In case
of accident to one or two chambers, the one or two remaining tight
will still float the whole and save the passengers.

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

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

Here among the rubbish are some shriveled wild grapes also. As we
shall see elsewhere, their best scheme is to be eaten by certain birds,
which do not digest their bony seeds; but in case some of them are
left there is another mode of travel, not by wings of a bird, but
by floating on water.

[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 dogwoods
are eaten for the pulp by birds, but in case any are left they behave
after the manner of grapes.

14. Bits of cork around the seeds prevent them from
sinking.--Narrow-leaved dock is a prominent weed, and is especially
at home on river bottoms and on low land that is flooded once in a
while.

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

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

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

[Illustration: FIG. 18.--Fruit of Asa-Gray sedge with an inflated
sack 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. Now
we see the probable reason why the sack is inflated in some species
of 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 be
recognized by every one. They belong to the arrowhead, _Sagittaria_,
found in shallow ponds or slow streams. They are flattened, and on
one edge, or both, and at the apex is a spongy ridge. Very likely,
by this time, the reader has surmised that this serves the purpose
of a raft to float the small seed within, which would sink at once
if separated from the boat that grew on its margins. In this connection
may be studied achenes of water plantain, _Alisma_, bur reed,
cat-tail flag, arrow grass, burgrass, numerous pondweeds, several
buttercups, the hop, nettles, wood nettle, false nettle, cinquefoil,
avens, ninebark, buttonbush, and in fact a large number and variety
of plants usually found on river bottoms.

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

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

One of the lyme grasses, _Elymus Virqinicus_, is a stiff, short grass,
growing along streams. Each spikelet with its chaff adheres to two
empty glumes, stout, thick, and spongy, which make a safe double boat
for transportation down stream whenever the water is high enough.
The grains of rice-cut grass, grown in ditches and spring brooks,
sink if separated, but in the chaff, as they fall when ripe, they
are good floaters.

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

In the driftwood, which we still have under consideration, are some
fruits of maple, beech, oak, tulip tree, locust, and basswood. Maples
are well scattered by the wind, but these seed-like fruits have taken
to the water, and a few still retain vitality. An acorn, while yet
alive, sinks readily, and is not suited for water navigation, unless
by accident it rides on some driftwood. The fruits of the tulip tree,
locust, and basswood behave well on the water, as though designed
for the purpose, though we naturally, and with good reason, class
them with plants usually distributed by wind.

16. Fruit of basswood as a sailboat, and a few others as adapted to
the water.--In spring, when the bracts and fruits of the basswood
are dry and still hanging on the tree, if a quantity of them are shaken
off into the water which overflows the banks of a stream, many of
these, as they reach the water, will assume a position as follows:
The nuts spread right and left and float; the free portion of the
bract extends into the water, while the portion adhering to the
peduncle rises obliquely out of the water and serves as a sail to
draw along the trailing fruit. After sailing for perhaps fifteen
minutes, the whole bract and stem go under water, the nuts floating
the whole as they continue to drift with the wind.

Noticeable among seeds in the flood wood are some of the milkweeds,
which every one would say at a glance were especially fitted for
sailing through the air, aided by their numerous long, silky hairs.
These hairs are no hindrance to moving by water. I discovered one
little thing in reference to the seed which makes me think the Designer
intended it should to some extent be carried by water. The flat seed
has a margin, or hem, which must be an aid to the wind in driving
it about; but this margin is thickened somewhat by a spongy material.

[Illustration: FIG. 23.--Seed of milkweed with a corky margin
enabling 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 contain
considerable air in the middle, near where the seeds are placed, as
though the air was intended to support them on top of water.

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

These berries are  and edible--qualities that attract the
birds. And here we find in several places the bulblets of a wild garlic,
_Allium Canadense_, which grows on the river bottom. These bulblets
are produced on top of the stem with the flowers, and float on the
water. The seeds of the white water lilies, and yellow ones also,
by special arrangement float about on the water with the current or
the wind. The coffee tree grows rather sparingly along some of the
streams, and on moist land as far north as Clinton County, Michigan.
The stout, hard pods are three to four inches long, one and one-quarter
to one and one-half inches wide, and one-half inch thick. The very
hard seeds are surrounded with sweet pulp, which most likely made
it an inducement for some of our native animals to devour them and
thus transport the undigested seeds to remote localities. The pods
often remain on the trees all winter, and when dry, will float on
the water of overflowed streams without any injury resulting to the
hard seeds. By themselves the seeds sink at once.




CHAPTER V.
SEEDS TRANSPORTED BY WIND.


17. How pigweeds get about.--In winter we often see dead tops of
lamb's-quarters and amaranths--the smooth and the prickly
pigweeds--still standing where they grew in the summer. These are
favorite feeding grounds for several kinds of small birds, especially
when snow covers the ground.

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

18. Tumbleweeds.--Incidentally, the foregoing pages contain some
account of seeds and fruits that are carried by the aid of wind, in
connection with their distribution by other methods; but there are
good reasons for giving other examples of seeds carried by the wind.
There is a very common weed found on waste ground and also in fields
and gardens, which on good soil, with plenty of room and light, grows
much in the shape of a globe with a diameter of two to three feet.
It is called _Amaranthus albus_ in the books, and is one of the most
prominent of our tumbleweeds. It does not start in the spring from
seed till the weather becomes pretty warm. The leaves are small and
slender, the flowers very small, with no display, and surrounded by
little rigid, sharp-pointed bracts. When ripe in autumn, the dry,
incurved branches are quite stiff; the main stem near the ground
easily snaps off and leaves the light ball at the mercy of the winds.
Such a plant is especially at home on prairies or cleared fields,
where there are few large obstructions and where the wind has free
access.

The mother plant, now dead, toiled busily during the heat of summer
and produced thousands of little seeds. The best portion of her
substance went to produce these seeds, giving each a portion of rich
food for a start in life and wrapping each in a glossy black coat.
Now she is ready to sacrifice the rest of her body to be tumbled about,
broken in pieces, and scattered in every direction for the good of
her precious progeny, most of whom will find new places, where they
will stand a chance the next summer to grow into plants. Sometimes
the winds are not severe enough or long enough continued, and these
old skeletons are rolled into ditches, piled so high in great rows
or masses against fences that some are rolled over the rest and pass
on beyond. Occasionally some lodge in the tops of low trees, and many
are entangled by straggling bushes. In a day or two, or in a week,
or a month, the shifting wind may once more start these wrecks in
other directions, to be broken up and scatter seeds along their
pathway.

During the Middle Ages in southern Egypt and Arabia, and eastward,
a small plant, with most of the peculiarities of our tumbleweed just
described, was often seen, and was thought to be a great wonder. It
was called the "rose of Jericho," though it is not a rose at all,
but a first cousin to the mustard, and only a small affair at that,
scarcely as large as a cabbage head. A number of other plants of this
habit are well known on dry plains in various parts of the world;
one of the most prominent in the northern United States is called
the Russian thistle, which was introduced from Russia with flaxseed.
In Dakota, often two, three, or more grow into a community, making
when dry and mature a stiff ball two to three feet or more in diameter.

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

One of our peppergrasses, _Lepidium intermedium_, sometimes attains
the size and shape of a bushel basket; when ripe, it is blown about,
sowing seeds wherever it goes. The plants of the evening primrose
sometimes do likewise, also a spurge, _Euphorbia_ [_Preslii_]
_nutans_, a weed a foot to a foot and a half high.

Low hop clover, an annual with yellow flowers, which has been
naturalized from Europe, has developed recently on strong clay land
into a tumbleweed six inches in diameter. The tops of old witch grass,
_Panicum capillare_, and hair grass, _Agrostis hyemalis_, become
very brittle when ripe, and snap from the parent stem and tumble about
singly or in masses, scattering seeds by the millions. I have seen
piles of these thin tops larger than a load of hay where they had
blown against a grove of trees, and in some cases many were caught
in the tops of low trees.

[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 careful
observer with an eye to this subject will be rewarded by finding many
other plants that behave more or less as tumbleweeds. Especially is
this the case on prairies. These are annuals, and perish at the close
of the growing season. There are numerous other devices by which seeds
and fruit secure transportation by the wind.

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

[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 tossing
the half-pod a few feet, leaving it perhaps to be again and again
moved farther forward. The writer has seen these half-pods
transported by this means more than a block. But many of the pods
stick to the limbs till winter comes. Then a breeze tears off a few
pods and they fall on the snow, which has filled up all the crevices
in the grass and between the dead leaves and rubbish. Each half-pod,
freighted with every other seed, is admirably constructed; like an
ice boat, it has a sail always spread to the breeze. In this way there
is often nothing to hinder some of the seeds from going a mile or
two in a few minutes, now and then striking some object which jars
off a seed or two. The seeds are very hard, and no doubt purposely
so, that they may not be eaten by insects or birds; but once in moist
soil, the covering slowly swells and decays, allowing the young plant
to escape. Thus the locust seeds are provided with neither legs, wings,
fins, nor do they advertise by brilliant hue and sweet pulp; but they
travel in a way of their own, which is literally on the wings of the
wind.

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

21. Nuts of the basswood carried on the snow.--Here are some notes
concerning the distribution of the spherical nuts of basswood. The
small clusters of fruit project from a queer bract which remains
attached before and after falling from the tree.

[Illustration: FIG. 28.--Fruit and bract of basswood well adapted
for moving before the wind on the snow.]

This bract, when dead, is bent near the middle and more or less twisted,
with the edges curving toward the cluster of nuts. From two to five
nuts about the size of peas usually remain attached till winter, or
even a few till spring. This bract has attracted a good deal of
attention, and for a long time everybody wondered what could be its
use. We shall see. The cluster of nuts and the bract hang down,
dangling about with the least breath of wind, and rattling on the
trees because the enlarged base of the stem has all broken loose
excepting two slender, woody threads, which still hold fast. These
threads are of different degrees of strength; some break loose after
a few hard gales, while others are strong enough to endure many gales,
and thus they break off a few at a time. The distance to which the
fruit can be carried depends on the form of the bract, the velocity
of the wind, and the smoothness of the surface on which the fruit
falls. When torn from the tree the twist in the bract enables the
wind to keep the cluster rapidly whirling around, and by whirling
it is enabled to remain longer suspended in the air and thus increase
the chances for a long journey. In throwing some of these from a
third-story window, it was found that a bract with no fruit attached
would reach the ground sooner than a bract that bore from two to four
solid nuts. The empty or unloaded bracts tumble and slide through
the air endwise, with nothing to balance them or steady their descent,
while the fruit on other bracts holds them with one side to the air,
which prolongs their descent. The less a loaded bract whirls, the
faster its descent, and the more a bract whirls when the wind blows,
the farther it is carried. The bract that is weighted with a load
of fruit acts as a kite held back by a string, and when in this position
the wind lifts the whole as well as carries it along. Before snow
had fallen in 1896, by repeated moves on a well-mowed lawn, fruit
and bracts were carried about two hundred feet, while with snow on
the ground the distance was almost unlimited, excepting where there
were obstructions, such as bushes and fences. When there is a crust
on the snow and a good wind, the conditions are almost perfect. Over
the snow the wind drives the bracts, which drag along the branch of
fruit much as a sail propels a boat. The curving of the edges of the
bract toward the fruit enables the wind to catch it all the better,
and to lift it more or less from the snow. With changes in the direction
of the wind, there is an opportunity for the fruit of a single tree,
if not too much crowded by others, to spread in all directions. After
watching these maneuvers, no one could doubt the object of the bent
bracts of the basswood, and as these vary much in length and width
and shape on different trees, it would seem that perhaps nature is
still experimenting with a view to finding the most perfect structure
for the purpose.

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

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

22. Buttonwood balls.--Nature seems to have no end of devices for
sowing seeds to advantage. Here is one which always interests me.
The fruit of the buttonwood, or sycamore, which grows along streams,
is in the form of balls an inch and a half in diameter. These balls
grow on the tops of the highest branches, and hold on into winter
or longer. The stems are about two inches long, and soon after drying,
through the action of the winds, they become very flexible, each
resembling a cluster of tough strings. The slightest breeze moves
them, and they bob around against each other and the small branches
in an odd sort of way. After so much threshing that they can hold
no longer, the little nuts become loosened and begin to drop off a
few at a time. Certain birds eat a few and loosen others, which escape.
The illustration shows some of these nuts, each supplied with a ring
of bristles about the base, which acts as a parachute to permit the
wind the easier to carry them for some distance before falling, or
to drift them on the surface of the snow or ice.

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

23. Seeds that tempt the wind by spreading their sails.--On low lands
in 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 pink
flowers. In mellow soil the slender rootstocks spread extensively,
and each year new sprouts spring up all around, six to eight feet
distant. Below each flower ripens a long, slender pod, which splits
open from the top into four parts, that slowly curve away from a
central column. The apex of each seed is provided with a cluster of
white silky hairs nearly half an inch long.

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

The tips of the hairs stick slightly to the inside of the recurved
valves, some hairs to one valve, and often others to the adjacent
valve, thus spreading them apart with the seed suspended between.
Four rows of the seeds are thus held out at one time. Often not over
half, or even a tenth part, of the seeds are well developed, yet the
silky hairs are present and float away in clusters, thus helping to
buoy those that are heavy. This is a capital scheme, for when the
pods are dry and unfurled, they silently indicate to the slightest
breath of air that they are ready for a flight, and it doesn't take
much to carry them for a long distance. As an active boy delights
to venture again and again over thin ice on a shallow pond in the
pasture, half fearing, yet half hoping, that he may become a hero
by breaking through and escaping, so likewise many of these seeds
and seed-like fruits spread themselves out, as if to tempt the wind
to come along and attack them.

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

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

24. Why are some seeds so small?--Do you know why so many kinds of
plants produce very small and light seeds? Would it not be better
if they produced fewer and larger seeds, which would then be stronger
and better able to grow under adverse conditions? But a large number
of small seeds cost the plant no more effort than a small number of
large ones, and the lighter and smaller the seeds and the more there
are of them, the better their chances for distribution, especially
for long distances. The minute size of spores of most of the fungi
are 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 the
race track? That the animal may have less weight to carry and thereby
use his surplus strength in making better time. The less weight the
parachute of the seed of the willow-herb has to carry, the greater
the chances for success in making a long journey. Of the willow-herb
it takes one hundred seeds to weigh a milligram, including the hairs
attached to them, and it would take thirty thousand to weigh as much
as an ordinary white bean.

25. Seeds with parachutes.--Many years ago large portions of Huron
and Sanilac counties of eastern Michigan were swept by a fire so severe
that the timber was all killed. Fifteen years later the woody growth
consisted mostly of willows, poplars, and birches. The seeds of all
kinds of willows and poplars are very light, and are produced in
immense quantities. Like those of the great willow-herb, they are
beautifully constructed for making long journeys through the air--a
fact that explains the frequency of these trees in burned districts.
A considerable number of seeds and fruits grow with a parachute
attached at one end, not to prevent injury by falling from the tree
top, but to enable the wind to sustain and transport them for a longer
distance.

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

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

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 row
has a very important duty yet to perform in guarding the large family
within. At night, or in daytime, if the day be wet, the long scales
press like a blanket closely about the flowers, and do not permit
them to come out; but when the sun is bright, it shrinks the outer
side of these scales, which then curl apart, leaving the yellow
flowers ready for bees to visit or boys to admire and study. For
several days the flowers of a head blossom in succession, each night
to be snugly wrapped by the scales, and the next day to be again left
open, if the weather be fine. After each flower in turn has been
allowed to see the light, and after all have been crawled over by
bee 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 while
receiving food from the mother plant to perfect each little fruit
and seed. During all this period of maturing, day and night, rain
or shine, the scales hold the cluster closely; the stem bends over
to one side, and the rain and dew is kept from entering. After a while,
on some bright morning, the dandelion stalk is seen standing erect
again, 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 attached
to the seed-like fruit below spreads out, and the community, which
now looks like a white ball of down, is ready for a breeze. The feathery
top is now ready to act as a parachute, and invites the wind to catch
up the whole and float it away. If there is no breeze, the moist air
of 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, some
anemones, smoke tree, virgin's bower, and some of the grasses.

27. How the lily sows its seeds.--Ripened pods of lilies usually stand
straight up on a stiff, elastic stem; beginning at the top, each one
slowly splits into three parts, which gradually separate from each
other. 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 does
not 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 opening
to permit seeds to dry and the wind to enter; to the right, a fruit
later in the season. Two views of a flat seed.]

Observe that the three opening cells are lashed together loosely with
a latticework. No slight breeze can dislodge the seeds, but just see
how they behave in a good gale! The elastic stems are swayed back
and forth against each other, and some of the upper seeds are tossed
out by the wind that passes through the lattice, and at such times
are 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 away
the first or even the second time, and as succeeding breezes may come
from different directions, it is thus possible for the lily to scatter
its seeds in all directions.

The seeds of the lily are flat, very thin, and rather light, not
designed to be shot out like bullets, but to be carried a little way
by the wind; the pods are erect, and open at the top, that the seeds
need not escape when there is no wind or unless some animal gives
the stem a strong shake. The latticework was made for a purpose, and
the gradual opening of the pods prevents the supply from all going
in one direction or in one day, for a better day may arrive. The student
will 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 large
ripe pod of the poppy stands erect on a stiff stem, with a number
of small openings near the top. The seeds are nearly spherical, and
escape, a few at a time, when the stem is shaken by the wind or some
animal, thus holding a reserve for a change of conditions. Here is
an 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 holes
opening when dry to allow seeds to be shaken out.]

The small holes are still uppermost, but to be uppermost in this case
it 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 covered
with a hood, umbrella, or shed, so that seeds may be kept continually
dry 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, enclosed
by a five-parted, bladdery inflated calyx." The margins of the lobes
of the calyx curl upwards and outwards as the berry hangs with the
apex downward.

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

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

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

The berry is as large as one's thumb, and when ripe, bursts open
irregularly on the upper side as it hangs up under the calyx. As the
covering of the pod opens more and more, a few seeds at a time may
be 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 them
about. Water does not seem to get into the berries even when they
are torn open, for when it is poured over the branches it rolls off
the calyx roof as freely as from a duck's back. The fruits of
_Physalis_ are apparently kept dry in a manner similar to the apple
of 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, and
most other mints, remains dry and stiff, as a cup to hold one to four
little round nutlets as they ripen. The figure shows two of these
in section, as they are attached to the main stem of the plant, or
one of its branches. Observe the direction taken by the upper and
by the lower points of the calyx. When dry, the plant behaves somewhat
as follows: when the wind jostles the branches against each other,
or when an animal of some kind hits the plant, this movement causes
many of these cups to get caught; but the elastic stem comes suddenly
back to its place, and in so doing flips a nutlet or more from its
mouth one to six feet, somewhat as a boy would flip a pea with a
pea-shooter. In our garden, July 2, when plants of sage, _Salvia
interrupta_, were ripening their fruit, we found it difficult to
collect any seeds, but seedlings were observed in abundance on every
side of the plant, some to the distance of six feet. Plants dispersing
seeds in this manner have been called catapult fruits. Examine
ripening fruits of blue curls, pennyroyal, germander, balm,
horehound, dittany, hyssop, basil, marjoram, thyme, savory, catmint,
skullcap, self-heal, dragon's head, motherwort, and various dry
fruits 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 the
grains of grasses are invested with glumes, or chaff, and a
considerable per cent of the chaff has awns, some of which are well
developed and some poorly developed. The distribution of such grasses
depends on several agents--wind, water, and animals. The chaff and
awns of all are hygroscopic; that is, are changed by differences
caused by variation of moisture in the air. Sweet vernal grass, tall
oat grass, holy grass, redtop, animated or wild oats, blue-joint,
and porcupine grass are among them. When mature, the grain and glumes
drop off, or are pushed off, and go to the ground. When moist, these
awns untwist and straighten out, but when dry they coil up again;
with each change they seem to crawl about on the ground and work down
to low places or get into all sorts of cracks and crevices, where
the first rain is likely to cover them more or less with earth, after
which 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 more
particularly on the dry prairies of the central portion of the United
States. This grass, when ripe, has a very bad reputation among
ranchmen for the annoyance the bearded grain causes them. The grains
are blown into the stubble among grasses with the bearded point down,
sticking into the soil. The first rain or heavy dew straightens out
the awns, which are twisted again as they dry. The bearded point works
a little farther with each change, and after twisting and untwisting
a 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 the
ground. But this is not all. The grains are quick to catch fast to
clothing, as people move among the plants, and they are admirably
fitted for attaching themselves to dogs and sheep, which they annoy
very much. These animals transport the grains for long distances.
The twisting and untwisting of the awns enable the grain to bore
through the fleeces, and even to penetrate the skins and make wounds
which sometimes cause the death of the animal. Examine also seeds
of pin clover, Alfilerilla, which is becoming abundant in many parts
of 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 of
the silver maple falls in summer. As these trees are most abundant
along the margins of streams, the fruit often drops into the water
and is carried down stream to some sand drift or into the mud, where
more 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 strong
breeze, sometimes a whirlwind, has been seen to carry these mature
fruits 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 material
put in the form of a ball. On the same principle, many seeds and fruits
are flattened, apparently for a purpose; not that they may be easily
shot through the air by some elastic force, not to increase their
chances for attachment to animals, but to enable the wind to sustain
them the longer and carry them farther. Some seeds and dry fruits
are said to have wings, with the general understanding that they are
by this means better fitted to be sustained in air. We shall find
that all or nearly all flattened seeds and dry fruits, also winged
seeds and fruits, are one-sided, unbalanced, and more or less
twisted; consequently, in falling to the ground they whirl about,
and are thus kept much longer in the air than they would be if shaped
more like a winged arrow. Even the wings on the fruit of some of the
ashes are twisted, though many of them are flat. Experiments with
these things are sure to interest inquisitive children, or even older
persons, when once started right; they are likely to prove as
interesting as flying kites, skating, fishing, or coasting on the
hillside. Try experiments with seeds of catalpa, trumpet-creeper,
wild yam, pine, spruce, arbor vitae, 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 familiar
or not. No two of them will behave in all respects alike.

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

34. Plants which preserve a portion of their seeds for an
emergency.--Many a great general or business man has learned by
experience and observation that it is usually unwise to exhaust all
resources in one effort. If possible, he always plans to have
something in reserve for an emergency--a loophole for escape from
difficulty. We have seen in many instances that plants are endowed
with the same trait. This is well illustrated by the way in which
the jack-pine, _Pinus_ [_Banksiana_] _divaricata_, holds in reserve
a portion of its seeds, to be used in case the parent trees are killed
by fire. In 1888 I made a study of this tree as it lives on the sandy
plains of Michigan. The tree is often killed by fire, and never sprouts
from 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 only
a few years old, perhaps as young as five years in some instances.
The cones open slowly to liberate their seeds, some of them only after
months or even years, and in some cases they never open at all. I
have seen cones containing good seeds that had been nearly grown over
by the tree. Dry weather, the dryer and hotter the better, causes
many of these stubborn old cones to open their scales and allow the
seeds 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 the
trunks of trees are blackened, and by lack of reflection the heat
of the sun is rendered more intense; besides, the heat of the fire
acts 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 slowly
opened and begun scattering seeds on the vacant and newly burned
ground, at a time when there is the best possible chance for them
to 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 a
dark sheet-iron dish and exposed to the sun. The extra heat caused
the cones to open; many seeds were obtained and sown, and in five
days they began to come up, 95 per cent germinating. From the same
tree I selected at the same time older cones, which I believe to be
from 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 its
seeds, often for several years.]

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




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


By numerous devices a large number of the lower plants send off their
ripe spores with considerable force. Some call them sling fruits.
One in particular, _Pilobolus cristallinus_, found about damp
stables, I have observed to shoot black masses of spores to a spot
on a wall six feet above the ground, with enough force to have carried
them not less than twelve feet. When ripe and dry, the spores of most
ferns are shot from the parent plant by a motion forcible enough not
only 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 while
shooting 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 of
the Chinese wistaria, and left them on my desk in the library for
the night. The house was heated by a hot-air furnace. In the morning
the pods were in great confusion; most of them had split and curled
up, and the seeds were scattered all about the room. As usual the
little daughter, an only child, was accused of spoiling my specimens,
but she showed her innocence. A little investigation and a few
experiments with some pods not yet opened explained the whole matter
satisfactorily. The stout pods grow and ripen in a highly strained
condition, with a strong tendency to burst spirally, the two
half-pods being ready to coil and spring in opposite directions; when
the valves can no longer hold together, they snap with a sharp noise
and 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, and
then send them forth to seek their fortunes, so for months the mother
plant had labored, had produced and matured seeds, which at last it
scattered broadcast. Goethe, Kerner von Marilaun, each independently,
and very likely others, had an experience with ripe pods brought to
a warm room very similar to my own. In many cases the ripe and drying
fruits are "touched off" by wind jostling the branches or by animals
passing among them; in the latter case there is a chance that a portion
of the discharges will be lodged somewhere on the animal and be carried
along with it.

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

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

[Illustration: FIG. 47.--Fruit of violet partially dried and split
into three pieces, each piece pinching the seeds so closely that
sooner 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 with
what he reads and sees pictured, but has a strong desire to learn
how plants are made and how they behave. A considerable number of
seed 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 the
mustards 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 a
hard, woody, nut-like fruit, as large as a hazelnut; when ripe, the
apex gaps open more and more, the sides pressing harder against each
smooth seed, till finally it is shot, sometimes for a distance of
thirty feet. The girl who has shot an apple seed or lemon seed with
pressure of thumb and finger across a small room, can understand the
force needed to shoot a seed but little heavier than that of the apple
two 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 are
severed from the parent bush or tree and fall to the ground among
the leaves.

37. Squirrels leave nuts in queer places and plant some of them.--Even
before the arrival of frosts many of these are dropped by the aid
of squirrels, gray and red, which cut the stems with their teeth.
The leaves, with the help of the shifting winds, gently cover the
fruit, or some portions of it, and make the best kind of protection
from dry air and severe cold; and they come just in the nick of time.
Dame Nature is generous. She produces an abundance; enough to seed
the earth and enough to feed the squirrels, birds, and some other
animals. The squirrels eat many nuts, but I have seen them carry a
portion for some distance in several directions, and plant one or
two or three in a place, covering them well with soil. It may be the
thought of the squirrel--I cannot read his thoughts--to return at
some future time of need, as he often does. But in some cases he forgets
the locality, or does not return because he has stored up more than
he needs; or in some cases the squirrels leave that locality or are
killed; in any such case the planted nuts are not disturbed. At all
events, some of the nuts--one now and then is all that is needed--are
allowed to remain where planted. In this way the squirrel is a benefit
to 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 arbor
day comes in autumn, and he needs no message from the governor to
stimulate him to work.

After some red squirrels had been given black walnuts, a member of
my family saw them hide the nuts in all conceivable places, and in
some instances place them above a cluster of small branches of a tree
for support where three or more twigs spread from nearly the same
place. Here the nuts, one in a place, were left till perhaps shaken
to 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 one
neighborhood of Michigan, where something had placed a single walnut
or acorn in the forks of small branches. In some cases a severe wind
could have dislodged the nut.

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

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

The oak was an inch and a half in diameter, and the nut was about
six feet from the ground. The nearest bearing tree was fully three
hundred long steps distant. We can imagine that, through fright or
other causes, a squirrel might be suddenly interrupted while carrying
nuts, and might then drop them to the ground, where later a tree would
be started.

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

[Footnote 3: In the fall of 1897, Prof. C. F. Wheeler saw a blue jay
fly from a white oak tree with an acorn in its mouth. The bird went
to the ground four or five rods distant and crowded the acorn into
the 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 walnut
in the forks of several small branches.]

Some friends of mine collected a quantity of hazelnuts, while yet
the green husks enclosed the nuts, and placed them near the house
to dry. At once they were discovered by a blue jay, which picked out
a nut at a time, flew away, held the nut between its toes, cracked
it from the small end, and ate the contents. In this operation a number
of nuts slipped away and were lost. But it seems that all were not
eaten, for the next season half a dozen or more hazel shoots came
up, and to-day a new patch of hazel bushes is growing in the yard.
Doubtless many acorns are carried from place to place and dropped
in an aimless way by woodpeckers, blue jays, and crows; also beechnuts
by these birds, and by nuthatches, and by pigeons, before the latter
became nearly extinct. Woodpeckers and blue jays place beechnuts and
small acorns in the crevices of bark on standing trees. If left there
very long, the nuts will become too dry to grow, but in the act of
transporting them some of the nuts may be accidentally dropped in
various places.

39. Do birds digest all they eat?--To determine whether seeds would
lose their vitality in passing through the digestive organs of birds,
Kerner von Marilaun fed seeds of two hundred and fifty different
species 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 to
marmot, horse, ox, and pig, making five hundred and twenty separate
experiments. As to the marmot, horse, ox, and pig, almost all the
fruits and seeds were destroyed. From the ox grew a very few seeds
of millet, and from the horse one or two lentils and a few oats; from
the pig a species of dogwood, privet, mallow, radish, and common
locust. Under ordinary conditions, no seed was found to germinate
after passing through the turkey, hen, pigeon, crossbill, bullfinch,
goldfinch, nutcracker, titmouse, and the duck. Ravens and jackdaws
passed without injury seeds of stone fruits and others with very hard
coats. Of seeds that passed through the blackbird 75 per cent
germinated, 85 per cent in the case of the thrush, 80 per cent in
the case of the robin.[4]

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

40. Color, odor, and pleasant taste of fruits are advertisements.--In
summer, buds are formed on bushes of black raspberry, blossoms appear,
and these are followed by small, green, and bitter berries, which
hardly 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 where
they are and when they are fit to eat? The plant has enterprise and
has displayed two want advertisements by painting the berries first
dark red, and then dark purple, when they are good to eat. But is
the plant made expressly to produce berries, just to feed birds and
children? If that be all, why are seeds formed in the berries in such
large numbers? No! They produce berries that contain seeds, and from
these seeds are to grow more bushes. Then why should not the berries
always remain bitter or hard, so that nothing would touch them? If
we may say so, the plant produces sweet and showy berries on purpose
to be eaten, that the seeds may be carried away. What becomes of the
seeds? Each one is enclosed in a hard, tough covering, which protects
it from destruction in the stomachs of many birds and some other
animals. The seeds are well distributed by the animals that eat the
berries. 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 birds
for 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 colors
to attract attention. You see, then, that although the old parent
bush cannot change its place, young bushes grow from the tips of the
branches, and seedlings spring up at long distances from their old
homes.

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

Sparrows, finches, and similar birds in the winter eat and destroy
seeds of grasses and weeds, while the same birds in summer and autumn
eat bushels of blueberries, huckleberries, elderberries,
raspberries, strawberries, and similar fruits, and distribute their
unharmed seeds over thousands of acres, which otherwise might never
support a growth of these species.

The downy woodpecker, among other things, devours berries of three
kinds 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 as
those of spicebush, sour gum, cherries, grapes, blackberries. The
flicker devours most of the fruits listed for the two woodpeckers
named above, also hackberry, black alder, green brier, bayberries.
A number of other woodpeckers possess habits much the same as the
three above named. The cedar bird devours many species of hard-seeded
fruits.

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. Where
the leaves are liable to become red in autumn the berries are often
blue. Of such, notice wild grapes, blueberries, and berries of
sassafras, though the flowering dogwood has red leaves as well as
red berries.

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

41. The meddlesome crow lends a hand.--"One of the most industrious
and persistent seed-transporting agencies I know of is that
ubiquitous, energetic, rollicking, meddlesome busybody, the crow.
I have seen crows gather by hundreds and have a regular powwow, a
mass convention, where they seemed to discuss measures and appoint
officers. At length they get through, and as they start to fly away
many, 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, which
he may carry five miles and light on a beech tree where something
else will attract his attention, when he will drop the acorn and maybe
pluck a pod of beechnuts and fly away somewhere else."--_Prof.
W. B. Barrows_.

The number of seeds distributed by crows is enormous, and consists
of 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, shown
in the illustration, and germinate more promptly than those untouched
by birds.

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

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

42. Ants distribute some kinds of seeds.--Ants are numerous, strong,
skillful, and in suitable weather are always very busy. Their habits
have been investigated, and it has been found that in some respects
they are genuine farmers on a small scale. They have their slaves
(not hired help); they feed their plant lice, remove them from place
to place, and otherwise care for them, because the lice constitute
one of the chief sources of their supply of sweet. They build roads
and houses, and enjoy society after their fashion. They have use for
certain kinds of seeds, portions or all of which they eat at once
or carry to their homes. A number of persons in different countries
and at different times have seen ants carrying seeds. Some young
student of botany may have noticed along one side of the glossy seeds
of the bloodroot a delicate, fleshy ridge, and wondered what could
be 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 frequently
happens, carry such seeds to their homes. The smooth seeds they do
not eat, but cast them out of their nests after using the part they
like; 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 species
of 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 take
the seed.]

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

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

43. Cattle carry away living plants and seeds.--In Arizona, where
cacti abound, Professor Toumey finds that many of them are broken
in pieces by cattle, which eat a portion, while other portions often
adhere to the legs or noses and are carried from place to place. These
fragments are usually capable of growing.

The unicorn plant, _Martynia proboscidia_, common in the
southwestern portion of the United States, is sometimes seen in
cultivation. When ripe, the fruit is hard, carrying two stout beaks
with recurved tips. Experiments show it to be admirably adapted to
catch on to the feet of sheep, goats, and cattle, or hold to the fleeces
of the two former.

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

44. Water-fowl and muskrats carry seeds in mud.--Seeds and fruits
of aquatic and bog plants that are floating, or in the mud of shallow
water, are often carried by ducks, herons, swallows, muskrats, and
other frequenters of such places, on their feet, beaks, or feathers,
as they hastily leave one place for another. In this way seeds of
water plantain, sedges, grasses, rushes, docks, arrowhead, pondweeds,
duckweed, cat-tail flag, bur reed, bladderwort, water crowfoot, and
many others are transported from one pond, lake, or stream, to another.
In some cases enough of a living plant may be detached and carried
away to keep on growing. Darwin found on the feet of some birds six
and three-quarter ounces of mud, in which were five hundred and
thirty-seven seeds that germinated. Mud may be carried on the feet
of land animals as well as on aquatic animals, not only from ponds
and bogs, but from the fields where seeds may have accumulated in
the earth or washed down the <DW72>s.

45. Why some seeds are sticky.--Some seeds and fruits are sticky;
in some instances the mucilaginous substance is normally moist enough
to adhere to anything that touches it, while in other cases it requires
to 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 berries
of some plants, when fully ripe, burst very easily when touched, and
some of the seeds are then likely to adhere to animals and be carried
away. Some berries of several plants belonging to the nightshade
family have this peculiarity, as well as some of the cucurbits. When
the outer covering of seeds of water lilies, arums, and others are
broken, the gummy secretion is very likely to adhere to the feathers,
or fur, or feet of animals. A number of fruits, and even the upper
fruit-bearing branches, have sticky glands with which to catch on
to any passing object. Among these are some kinds of sedges,
chickweeds, and catchflies.

The sticky substance on seeds and fruits not unfrequently serves
another good turn besides enabling them to adhere to animals. The
slime holds them to the spot where they are to grow, or it enables
some to float or to sink in water, according to the amount of the
mucilage.

46. Three devices of Virginia knotweed.--A perennial plant, four to
five feet high, grows on low land, usually in the shade. It is
_Polygonum Virginicum_, and so far without a common name, unless
Virginia knotweed be satisfactory. It is a near relative of knot grass
and smartweed and Prince's feather. The small flowers are borne on
a long, elastic, and rather stiff stem, and each flower stalk has
a joint just at the base. As this fruit matures, the joint becomes
very 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 shaking
produced by the wind jostling several against each other is
sufficient to send off a number of ripe fruits in every direction.
Like many other plants we have seen, this has more than one way of
scattering seeds, and often more than two ways. Observe the slender,
stiff beak, terminating in two recurved points. Let a person or some
animal pass into a patch of these plants, and at once numerous fruits
catch on wherever there is a chance, and some are shot upon or into
the fleeces of animals, there to find free transportation for
uncertain distances. Should there be a freshet, some of these fruits
will float; or, in case of shallow currents after a rain, some of
them are washed away from the parent plant. Any inquisitive person
cannot fail to be pleased if he experiment with the plant when the
fruit is ripe.

[Illustration: FIG. 55.--Fruit of Virginia knotweed ready to shoot
off 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 number
of rather weedy-looking herbs, common to woods or low land, known
as Avens, _Geum_. They are closely allied to cinquefoil, and all
belong to the rose family. The slender stiles above the seed-like
ovaries of some species of Avens are described as not jointed, but
straight and feathery, well adapted, as we might suppose, to be
scattered 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. When
a whole bunch of pistils has drawn all the nourishment possible, or
all that is needed, from the plant mother, the upper part of each
stile drops off, leaving a sharp, stiff hook at the end. At this time
each pistil loosens from the torus and can be easily removed,
especially if some animal touch the hooks. To help in holding fast
to animals, there are a number of slender hairs farther down the stile,
which are liable to become more or less entangled in the animal's
hair, fur, wool, or feathers. Even in the small number of plants here
noticed, we have seen that scarcely any two of them agree in the
details of their devices for securing transportation of seeds. I know
of nothing else like the Geum we are now considering. When young and
green, the tip of each hook is securely protected by a knob or bunch,
with a little arm extending above, which effectually prevents the
hook from catching on to anything; but, when the fruit is ripe, the
projecting knob with its little attachment disappears. The figures
make further description unnecessary. To keep the plow from cutting
into the ground while going to or from the field, the farmer often
places a wooden block, or "shoe," over the point and below the plow.
Sometimes we have known persons to place knobs of brass or wood on
the tips of the sharp horns of some of their most active or vicious
cattle, to prevent them from hooking their associates or the persons
having them in charge. Nature furnishes the points of the young fruits
of some species of Avens with knobs, or shoes, for another purpose,
to benefit the plants without reference to the likes or dislikes of
animals.

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

48. Diversity of devices in the rose family for seed sowing.--All
botanists 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 close
relationship, the modes of seed dispersion are varied. The seeds of
plums and cherries and hawthorns are surrounded by a hard pit, or
stone, which protects the seeds, while animals eat the fleshy portion
of the fruit. When ripe, raspberries leave the dry receptacle and
look like miniature thimbles, while the blackberry is fleshy
throughout. The dry, seed-like fruits of the strawberry are carried
by 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, while
in Agrimony many hooks grow on the outside of the calyx and aid in
carrying the two or three seeds within. Plants of some other families
illustrate the great diversity of modes of dispersion as well as the
roses.

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

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

Many wild animals unwillingly carry about such fruits, and after a
while most of them remove what they can with claws, hoof, or teeth.
Many of these plants have no familiar common names, but who has not
heard of some of these? enchanter's nightshade, bedstraw, wild
liquorice, 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 very
large number of small seeds and fruits are rubbed off and carried
away by animals. Some of these stick by means of the pappus, as, for
instance, the dandelion, thistle, prickly lettuce; others by means
of hairs on the seed, such as those of the willow-herb and milkweeds
and willows; or by hairs on the fruit, as virgin's bower, anemone,
cotton grass, and cat-tail flag. These last named are apparently
designed to be wafted by the wind, but they are ever ready to improve
any other opportunity offered, whether it be by water or by clinging
to 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 two
barbed points.]

[Illustration: FIG. 60.--A fruit of tick-trefoil, _Desmodium_, and
a 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 where
they cannot germinate and produce plants, or fall in such numbers
that most of them in growing are crowded and starved to death. A very
small proportion fall on good ground, and succeed in becoming
fruiting plants. A large plant of purslane produces one million two
hundred and fifty thousand seeds; a patch of daisy fleabane, three
thousand seeds to each square inch of space covered by a plant. The
genuine student will not be satisfied till he has selected several
different kinds of plants and counted, or estimated, the number of
seeds produced by each, or the number of seeds furnished to the area
covered by one or by several plants.




CHAPTER VIII.
MAN DISPERSES SEEDS AND PLANTS.


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

51. Burs stick to clothing.--Late in summer or in autumn, who is there
who has not returned from a walk along the river or from a tramp through
thickets or the open woods, to find large numbers of half a dozen
kinds of seed-like fruits sticking to his clothes? When ripe, these
fruits usually separate from the parent plant very easily, by a joint
or 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 at
the end of the journey, or before, you sit down in some comfortable
spot and deliberately pick off the unwelcome stick-tights. At such
times you have been the means of transporting seeds, and you have
left them scattered about ready to grow. If you ever were so fortunate
as to live on a farm, you must have seen your father or his hired
help carefully look about the field or the wood lot and remove all
the bur-bearing plants that could be found before turning in his flock
of sheep or the colts and cattle; for if this were not done, he knows
that hair and mane will surely be disfigured, and that the wool will
be rendered unsalable. In removing the weeds he defeated the plans
of Nature in her devices for sowing seeds.

The agency of man in the distribution of plants exceeds in importance
that of all other means combined. He buys and sells seeds and plants,
and sends them to all parts of the habitable globe. He exterminates
many plants in large areas, and substitutes in large measure those
of his choice. Mixed with seeds of grasses, clovers, or grains, he
introduces 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 larger
than a seed of cockle.]

L. H. Dewey, in the Yearbook of the Department of Agriculture for
the year 1896, p. 276, says: "Cockle seeds are normally somewhat
smaller than wheat grains. In some parts of the northwest, where wheat
for sowing has been cleaned year after year by steam threshers, all
the cockle seeds except the largest ones have been removed, and these
have been sown until a large-seeded strain has been bred which is
very difficult to separate from the wheat." For illustration, some
years ago I purchased of a dealer in Michigan a small quantity of
what was being sold on the market as seed of red clover; this specimen
contained 40 per cent of seeds of rib-grass or narrow-leaved
plantain.

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

Man introduces some seeds of weeds with unground feed stuff. He
introduces some with barnyard manure drawn from town. He gets some
in the packing of nursery stock, crockery, baled hay and straw. For
example, in 1895, baled hay from Kansas or that vicinity examined
at the Missouri Agricultural College was found to contain fifteen
species of weeds. Others from the west were examined in Michigan and
found to contain much foul stuff. Some are carried from farm to farm
by wagons, sleighs, or threshing machines; or they are spread by plows,
cultivators, and harrows. A few are introduced to grow for ornament
or food, and afterwards spread as weeds. A number have been shipped
to distant lands in the earth of ballast, which is often unloaded
and reloaded at wharves where freight is changed. They are carried
along the highway, strung along the towpath of canals, or are carried
in the trucks or in the cars of railroads. They are imported and
exported around the world in fleeces of wool. They float down
irrigating ditches from farm to farm, and with the water are well
distributed.

52. Man takes plants westward, though a few migrate eastward.--So
far as man's agency is concerned, the direction for plant migration
is generally westward, in the course taken by himself. In case of
two hundred kinds of weeds named by the United States Department of
Agriculture, one hundred and eight species are of foreign origin.
Three notable samples of weeds in the United States have gone from
the west to the east, carried in seeds of grasses or clovers. These
are _Rudbeckia hirta_, _Artemisia biennis_, _Plantago aristata_. To
these 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 is
an unwilling agent in distributing plants. Large volumes could be
filled with statements of man's more or less carefully planned
attempts to transport seeds and living plants from one part of the
world to another.




CHAPTER IX.
SOME REASONS FOR PLANT MIGRATION.


53. Plants are not charitable beings.--Man uses to his advantage a
large number of plants, but there appears to be no evidence that the
schemes for their dispersion were designed for anything except to
benefit the plants themselves. The elegant foliage and beautiful
flowers, the great diversity of attractive seeds and fruits, all
point 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 animals
without any compensation. By fertilizing flowers, by distributing
plants, and by other helpful acts, animals pay for at least a portion
of the damage they do.

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

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

55. Fruit grown in a new country is often fair.--Every horticulturist
knows that apples grown in a new country, that is suited to them,
are healthy and fair; but, sooner or later, the scab, and codling
moth, and bitter rot, and bark louse arrive, each to begin its
particular mode of attack. Peach trees in new places, remote from
others, are often easily grown and free from dangers; but soon will
arrive the yellows, borers, leaf curl, rot, and other enemies. For
a few years plums may be grown, in certain new localities, without
danger from curculio, or rot, or shot-hole fungus. It has long been
known 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 noticed
that, while pear-blight decimated or swept large portions of a pear
orchard, a few isolated trees, scattered about the neighborhood,
usually remain healthy. The virgin soil of the Dakotas produced, at
a trifling cost, healthy, clean wheat, but it was not long before
the Russian thistle, false flax, and other pests followed, to contest
their rights to the soil.

As animals starve out, in certain seasons when food is scarce, or
more likely migrate to regions which can afford food, so plants desert
worn-out land and seek fresh fields. As animals retreat to secluded
and isolated spots to escape their enemies, so, likewise, many plants
accomplish the same thing by sending out scouts in all directions
to find the best places; these scouts, it is needless to say, are
seeds, and when they have found a good place, they occupy it, without
waiting for further instructions.

56. Much remains to be discovered.--"In this, as in other branches
of science, we have made a beginning. We have learned just enough
to perceive how little we know. Our great masters in natural history
have immortalized themselves by their discoveries, but they have not
exhausted the field; and if seeds and fruits cannot vie with flowers
in the brilliance and color with which they decorate our gardens and
our fields, still they surely rival them--it would be impossible to
excel them--in the almost infinite variety of the problems they
present to us, the ingenuity, the interest, and the charm of the
beautiful contrivances which they offer for our study and our
admiration."[5]

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

Frequent rotations seem to be the rule for many plants, when left
to themselves in a state of nature. Confining to a permanent spot
invites parasites and other enemies, and a depleted soil, while
health and vigor are secured by frequent migrations. The more we study
in detail the methods of plant dispersion, the more we shall come
to agree with a statement made by Darwin concerning the devices for
securing cross-fertilization of flowers, that they "transcend, in
an incomparable degree, the contrivances and adaptations which the
most fertile imagination of the most imaginative man could suggest
with unlimited time at his disposal."[6]

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

Let no reader think that the topics here taken up are treated
exhaustively, for if he will go over any part of this work and verify
any 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 JOHN
T. CAMPBELL. _Am. Nat._ Vol. xix, p. 337. 1885.

Report of the U. S. Commissioner of Agriculture for 1888. Article
on 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 of
Ornithology 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 of
Ornithology 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.

Seeds of the Violet and Other Plants as Projectiles. By MOSES N. ELROD,
M.D. _Am. Nat._ Vol. xiii, p. 93. 1879.

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. Bulletin
No. 17. Fargo, North Dakota.

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

Migration of Weeds. By L. H. DEWEY. Yearbook of the U. S. Department
of 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 of
Species. Vol. ii, pp. 790-885. Henry Holt & Co., New York. 1895.







End of the Project Gutenberg EBook of Seed Dispersal, by William J. Beal

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