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. Coons, bears, skunks,
and porcupines move from one neighborhood to another. When the
thickets disappear and hunters abound, wild turkeys and partridges
retreat on foot or by wing. When the leaves fall and the cold winds
blow, wild geese leave the lakes in secluded northern homes, and with
their families, reared during the summer, go south to spend the winter.
Turtles swim from pond to pond or crawl from the water to the sand
bank, where they lay and cover their eggs. Fishes swim up or down
the creek with changing seasons, or seek deep or shallow water as
their needs require. Beetles and butterflies, when young, crawl about
for food and shelter, and when older use their wings in going long
distances.
These examples only serve to recall to mind what every boy or girl
knows and has known ever since he can remember--that most animals
move about whenever they want to, or whenever other animals will let
them.
2. Some animals catch rides in one way or another.--Some small animals,
like lice, ticks, and tiny spiders, walk slowly and only for short
distances. If, because of scarcity of food, they are suddenly seized
with the desire to move for a long distance, what are they to do?
On such occasions ticks and lice watch quietly the first opportunity,
catch on to the feet of birds or flying insects or other animals which
may happen to come their way, and, like a boy catching on to a farmer's
sleigh, ride till they get far enough, then jump off or let go, to
explore the surrounding country and see whether it is fit to live
in. If for some reason a spider grows dissatisfied and wants to leave
the home spot, she climbs to the top of some object and spins out
a fine, long web; this floats in the air, and after a while becomes
so long and light that the wind will bear the thread and the spinner
for a considerable distance, no one knows how far. These facts about
lice and spiders show how wingless insects can go long distances
without wings of their own.
How is it with plants? The woods, fields, marshes, roadsides ever
abound with interesting objects provided with strange devices
waiting to be studied by inquisitive girls and boys in and out of
school, and this finding out of nature's puzzles is one of the deepest
pleasures of life.
How quickly a mould attacks and creeps or spreads through a basin
of berries every one knows. The mould is as much a plant as the bush
that produced the berries; it comes from a small spore, which takes
the place of a bud or sprout or seed. The decay of a tree begins where
a limb or root has been injured, and whether the timber is living
or dead, this decay results from the growth of some one or more low
forms of plant life which enter the timber in certain places and slowly
or quickly penetrate and affect other portions more or less remote.