Transcriber’s Notes
Text printed in italics has been transcribed _between underscores_.
Small capitals have been replaced with ALL CAPITALS.
More Transcriber’s Notes may be found at the end of this text.
[Illustration: Copyright 1900 by A. R. DUGMORE.
SNAPPING-TURTLES FIGHTING.]
INTELLIGENCE
IN
PLANTS AND ANIMALS
BEING A NEW EDITION OF THE AUTHOR’S
PRIVATELY ISSUED “SOUL AND IMMORTALITY”
BY
THOMAS G. GENTRY, Sc. D.
AUTHOR OF “LIFE-HISTORIES OF BIRDS OF EASTERN PENNSYLVANIA,”
“THE HOUSE SPARROW,” “NESTS AND EGGS OF BIRDS
OF THE UNITED STATES,” ETC., ETC., ETC.
NEW YORK
DOUBLEDAY, PAGE & CO.
1900
Copyright 1900,
BY
DOUBLEDAY, PAGE & CO.
TO
ALL HUMAN BEINGS
WHO ARE GOOD AND KIND
TO THE HUMBLEST OF GOD’S CREATURES
THIS VOLUME
IS MOST AFFECTIONATELY DEDICATED
BY THE AUTHOR.
“Every beast of the forest is mine, and the cattle upon a thousand
hills.
“I know all the fowls of the mountains: and the wild beasts of the
field are mine.”--Psalm 1:10, 11.
PREFACE.
Nothing is more charming to the mind of man than the study of Nature.
Religion, moderation and magnanimity have been made a part of his
inner being through her teachings, and the soul has been rescued by
her influence from obscurity. No longer doth man grovel in the dust,
seeking, animal-like, the gratification of low and base desires, as was
his wont, but on the wings of thought is enabled to soar to the very
gates of Heaven and hold communion with God.
Though made “a little lower than the angels,” yet, through the
mighty play of forces that have been at work in the world, which we,
in the latter half of this enlightened century, are just beginning
to recognize and comprehend, he has been lifted from the mire of
degradation and placed upon a higher social, intellectual, moral
and spiritual level. Out of the animal, in the scheme of Deity, the
spiritual system of things is to be elaborated, and not the animal out
of the spiritual. This natural world, so to speak, is the raw material
of the spiritual. Therefore, ere man can understand the spiritual,
he must understand the natural. Though his knowledge was at first
about material things, or such as pertained to natural phenomena, yet
from this through the ages has been builded, little by little, that
mountain-height of knowledge, intellectual and moral, which, if rightly
directed, is to bring him into fellowship with Deity. “As we have borne
the image of the earthy, we shall also bear the image of the heavenly,”
or, Lord from heaven.
When is considered, therefore, the immense good which the study and
investigation of nature have accomplished, it is not at all surprising
that the literature on the subject should be markedly in the ascendant.
Natural science bids fair to be in a preëminent degree the pursuit of
the coming man. There is no end to the books that have been written
upon the subject during the past few decades, if not by specialists,
but by men and women who have been well informed and who have made
themselves fully capable of contemplating understandingly the world
which lies about them.
Our libraries are to-day quite affluent in books that are the handmaids
of natural science. Michelet and Hugh Miller, in their day, opened
glorious new worlds before a rising generation, and that generation is
now doing excellent work under the inspiration of the impetus which it
then received. Tait, Balfour Stewart, Dawson, Gray, McCook, Thompson,
Scudder, Mrs. Treat, Olive Thorne Miller and others have done much
to continue the interest, pleasure and enthusiasm awakened by those
earlier writers, and even Darwin and Huxley themselves, in detailing
their experiments, have not scorned to bring their thoughts within the
range of narrower minds.
But in the popularization of natural science no man has done more than
Rev. J. G. Wood in his numerous works. Not only have his writings
created in thousands a taste for nature-studies, but they have been no
less the means of cultivating the observation, awakening enthusiasm
and directing effort in the lines of original research and discovery.
Certainly no one, as his many writings so abundantly attest, possessed
a larger fund of knowledge concerning the powers and capabilities of
the lower animals than this author. Few knew our domestic animals
better than he, and none was more capable of judging of the mental
and moral _status_ which they should occupy in the world of animals.
It is true that men and women, eminent in theology, literature and
science, had expressed a belief in the idea that the “latent powers and
capacities” of the lower animals might be developed in a future life,
but no one had felt secure enough in this belief to warrant more than a
passing thought or two upon the subject.
Bishop Butler, in his “Analogy of Religion,” undoubtedly believed
the lower animals capable of a future life. In speaking of them in
this connection in the opening of his work, he says: “It is said
these observations are equally applicable to brutes; and it is
thought an insuperable difficulty that they should be immortal, and
by consequence capable of everlasting happiness. And this manner of
expression is both invidious and weak; but the thing intended by
it is really no difficulty at all, either in the way of natural or
moral consideration.” Referring then to the undeveloped powers and
capacities of the so-called brutes, the Bishop could perceive no reason
why they should not attain their development in an existence beyond
the earth-life. It was in pursuance of this same train of thought that
Rev. J. G. Wood was led to show in a work, entitled “Man and Beast
Here and Hereafter,” that the lower animals do possess those mental
and moral characteristics--the attributes of reason, language, memory,
moral responsibility, unselfishness and love--which we admit in man
as belonging to the immortal spirit, rather than to the perishable
body. Having previously cleared away the difficulties which certain
passages in the Old Testament seemingly interposed, and proved that
the Scriptures do not deny futurity of life to lower animals, he very
naturally concluded that as man expects to retain these qualities in
the future life there is every reason to suppose that they may share
his immortality in the Hereafter as in the Now they are partakers of
his mortal nature.
Few minds, unswayed by thoughts materialistic, can study the living
works of God, whether vegetal or animal, and fail to be convinced that
they, as living exponents of Divine conceptions, are as needful in the
world of spirit as in the world of matter. While many are disposed to
believe that man will share the future life with beast, bird, insect
and such like, yet but few, if any, can be found who believe that
tree and shrub and flower will be there to continue the life begun on
earth and reach out to higher and fuller development. In announcing
this belief, the author but expresses a conviction as deep as any that
could occupy a human mind. The possession of soul and spirit can be
predicated no less of plants than of man and the lower animals. They
have all one breath or life and one spirit, and as such are living
souls, living, breathing frames or bodies of life. From being living,
breathing frames, and endowed with the same life and spirit as man and
the lower animals, they have all one destiny, for “all go unto one
place; all are of the dust, and all turn to dust again.” But of the new
life which Christ came down to earth to proffer to man that he might
inherit the kingdom of God. While to man it was only offered, and had
for its purpose the uplifting and improvement of his earth-life by
the promise of something higher and better to those who are accounted
worthy, yet there can be no doubt that it was equally intended through
his uplifting to place all the creatures of the earth over which he
was given dominion by God upon a more elevated and nobler plane, so
that those which had been profited in the earth-life by his beneficent
influence should become partakers with him in the new life, when Christ
shall “transfigure the body of our humiliation, that it may become
of like form with the body of His glory, by the power of that which
enables Him even to subdue all things to Himself.” As all existence
is a unit, which the author has taken especial pains through the body
of this book to impress upon the minds of his readers, it can hardly
be conceived that an all-wise God, who is infinite in love, mercy and
justice, would look to the preservation in a future state of but a very
small part of the life which He has been instrumental in placing upon
this earth. It would be more consistent with His attributes, and with
the scheme of development of life upon our planet, whereby life has
been progressive, the fittest only being allowed to survive, to have
provided in the grand plan of redemption, not merely the salvation of
the highest of earth-life, but of all life, the purest and the best,
that would represent in the heaven-life, in spiritualized form, the
highest living exponents of Divine ideas. No other belief accords so
well with the teachings of science and philosophy. In its acceptance,
for it makes all life related to the Divine life, can there be any hope
of escape from materialism, that curse of the age.
THOMAS G. GENTRY, SC. D.
PHILADELPHIA, FEBRUARY 28, 1897.
CONTENTS
PAGE
Preface 1
Life and Its Conditions 9
Plants that Feed on Insects 16
Slime-Animals 32
Primitive Lasso-Throwers 36
Five-Fingered Jack on the Oyster 41
Earth-worms in History 48
Fiddler-and Hermit-Crabs 70
Funnel-Web Builder 77
Book-Lovers 86
You-ee-up 90
Tower-Building Cicada 95
Honey-Dew 104
Milch-Cows of the Ants 108
Living Artillery 111
Bright and Shining Ones 115
Queen of American Silk-Spinners 121
Basket-Carriers 126
Honey-Producing Caterpillars 132
Hibernating Butterflies 144
Leaf-Cutter Bee 149
Battle Between Ants 153
Nest-Building Fishes 158
Slippery as an Eel 168
Rana and Bufo 174
Our Natural Enemies 186
House-Bearing Reptiles 198
Summer Duck 204
American Woodcock 210
Piping Plover 218
Bob White 222
Ruffed Grouse 230
An Old Acquaintance 240
American Osprey 245
Turkey Buzzard 252
Rare and Curious Nests 263
Strange Friendship 279
Nature’s Little Store-Keeper 285
Canine Sagacity 290
Feline Intelligence 295
Bright Little Cebidae 301
Untutored Man 309
Living Souls 316
Consciousness in Plants 323
Mind in Animals 344
Life Progressive 404
Survival of the Fittest 426
Man’s Preëminence 469
Future Life 479
LIST OF ILLUSTRATIONS.
PAGE
1 Portrait of Author Frontispiece
2 Venus’s Fly-trap 20
3 Round-Leaved Sundew 25
4 Protomyxa Feeding 34
5 Fresh-Water Hydra 37
6 Star-fish Opening an Oyster 45
7 Common Earth-worms 60
8 Fiddler-Crabs 72
9 Warty Hermit-Crabs 75
10 Agalena and Her Funnel-Web 79
11 Lepismas at Work 88
12 You-ee-up in His Den 91
13 Seventeen-year Cicada 97
14 New-born Cicada 99
15 Dome-like House of Cicada 101
16 Blossom of Cucurbita 105
17 Nest of Lasius 109
18 Brachinus Pursued by an Enemy 112
19 Common Tiger Beetle 117
20 American Luna Moth 123
21 House-builder Moth 129
22 Pseudargiolus Butterfly 134
23 Violacea Butterfly 138
24 Neglecta Butterfly 142
25 Mourning-Cloak Butterfly 146
26 Leaf-Cutter Bee at Work 150
27 Battle Between Ants 154
28 Nest of Common Sun-fish 159
29 Black-nosed Dace 163
30 Common American Eel 172
31 Rana Clamata, or Green Frog 177
32 Common American Toad 181
33 Northern Rattlesnake 189
34 Mother Black Snake 192
35 Summer Green Snake 195
36 Water Snake 196
37 Common Box Tortoise 201
38 Summer Ducks and Young 206
39 American Woodcock 214
40 Female Piping Plover 220
41 Home of Bob White 225
42 Ruffed Grouse in Spring-time 235
43 Mexican Wild Turkey 241
44 Nest of American Osprey 247
45 Female Turkey Buzzard Dining 259
46 Nest of the Robin 264
47 Red-winged Blackbird’s Nest 266
48 Double Nest of Orchard Oriole 268
49 Female Baltimore Oriole 270
50 Acadian Flycatchers 272
51 Long-billed Marsh Wrens 274
52 Golden-Crowned Kinglets 275
53 Lace Hammock of Parula Warbler 276
54 Three-story Nest of Yellow Warbler 278
55 Saw-whet Owl and Chickaree Squirrel 282
56 Hackee, or Chipping Squirrel 287
57 My Dog Frisky 292
58 Tom on Duty 297
59 Jack at Dinner 305
60 Australian at Home 311
61 Representative Life of Western Asia 319
62 Seedling of Winter Grape 325
63 Tip of Radicle of Seedling Maple 331
64 Wonderful Equine Intelligence 347
65 Papier-Maché Palace of the Hornet 353
66 Unsolicited and Unlooked-for Kindness 357
67 Exhibition of Grandeur 378
68 Four Orphaned Robins 389
69 Mated for Life 396
70 Evidence of Conjugal Affection 400
71 Life in the Primordial Sea 410
72 Carboniferous Times 412
73 Mesozoic Flora and Fauna 415
74 Palæolithic Men Attacking Cave Bear 448
75 Era of Mind and Heart 462
FULL PAGE PLATES.
From Photographs from Nature by A. RADCLYFFE DUGMORE.
1 Snapping Turtles Fighting Frontispiece
FACING PAGE
2 Crab Waiting for Food Under a Rock 74
3 Box-tortoise Feeding on Fungus 200
4 Woodcock on Nest (showing protective coloring) 212
5 Red-eyed Vireo’s Two-Storied Nest With Cow-bird’s egg beneath 264
6 Long-billed Marsh Wren’s Nest 272
7 Chipping Squirrels Feeding 286
8 Wood Thrush Setting 402
LIFE AND IMMORTALITY.
LIFE AND ITS CONDITIONS.
All natural objects, roughly divided, arrange themselves into three
groups, constituting the so-called Mineral, Vegetable and Animal
kingdoms. Mineral bodies are all devoid of life. They consist of
either a single element, or, if combined, occur in nature in the form
of simple compounds, composed of more than two or three elements.
They are homogeneous in texture, or, when unmixed, formed of similar
particles which have no definite relations to one another. In form they
are either altogether indefinite, when they are said to be amorphous,
or have a definite shape, called crystalline, in which case they
are ordinarily bounded by plane surfaces and straight lines. When
mineral bodies increase in size, as crystals may do, the increase is
produced simply by accretion. They exhibit purely physical and chemical
phenomena, and show no tendency to periodic changes of any kind.
Fossils or petrifactions, which owe their existence and characters to
beings which lived in former periods of the earth’s history, cannot,
though made up of mineral matter, be properly said to belong to the
mineral kingdom.
But objects belonging to the vegetable and animal kingdoms differ
markedly from inert, lifeless, mineral matter. Carbon, hydrogen, oxygen
and nitrogen are the most important of the few chemical elements which
enter into their composition, and these elements are combined into
complex organic compounds, which always contain a large percentage of
water, are very unstable, and prone to spontaneous decomposition. They
are composed of heterogeneous, but related, parts, termed organs, the
objects possessing them being called organized bodies. Some of the
lowest forms of animals have bodies whose substance is so uniform that
they exhibit no definite organs, but this exception does not affect
the general value of this distinction. They are always more or less
definite in shape, presenting concave and convex surfaces, and being
limited by curved lines. When they increase in size, or grow, as we
properly term it, it is not by the addition of particles from the
outside, but by the reception of foreign matter into their interior and
its consequent assimilation. Certain periodic changes, which follow
a definite and discoverable order, are invariably passed through by
organized bodies. These changes constitute what is known as life. All
the objects, then, which fulfil these conditions are said to be alive,
and they all appertain either to the vegetable or the animal kingdom.
The study of living objects, no matter to which kingdom they belong,
is therefore conveniently called by the general name of Biology, which
means a discourse on life. And as all living objects may be referred to
one or other of these kingdoms, so Biology may be divided into Botany,
which treats of plants, and Zoölogy, which treats of animals.
Now that we have divided all organized bodies into plants and animals,
it becomes necessary to inquire into the differences which subsist
between them, and which will enable us to separate the kindred
sciences of Botany and Zoölogy. Nothing was thought so easy by older
observers than the determination of the animal or vegetable nature
of any given organism, but, in point of fact, no hard-and-fast line
can be drawn, in the existing state of our knowledge, between the
animal and vegetable kingdoms, and it is sometimes difficult, or even
impossible, to decide with positiveness whether we are dealing with a
plant or an animal. In the higher orders of the two kingdoms there is
no difficulty in reaching a decision, the higher animals being readily
separated from the higher plants by the possession of a nervous system,
of a locomotive power which can be voluntarily exercised, and of an
internal cavity adapted for the reception and digestion of solid food.
No so-called nervous system or organs of sense are possessed by the
higher plants, although some of them doubtlessly manifest conscious
and intelligent action, nor are they capable of voluntary changes of
place, nor provided with any definite internal cavity, their food being
generally fluid or gaseous.
Descending the scale to the very bottom, we reach a class of animals,
the Protozoa, which cannot be separated in many cases from the
Protophyta by these distinctions, since many of the former have
no digestive cavity, nor the slightest trace of a nervous system,
while many of the latter possess the power of active locomotion. As
to external configuration, no certain rules can be laid down for
separating animals and plants, many of the lower plants, either in
their earlier stages, or in their maturity, being exactly similar
in form to some of the lower animals. This is the case with some of
the Algæ, which resemble very closely in form certain Infusorian
animalcules. Again, many undoubted animals, which are rooted to solid
objects in their adult state, are so plant-like in appearance as
to be popularly regarded as vegetables. The Sea-firs, and the more
highly organized Flustras or Sea-mats, which are usually considered
as sea-weeds by sea-side visitors, are a few of many examples that
might be taken from the so-called Hydroid Zoöphytes. No decided
distinction between animals and plants can be drawn as to their minute
internal structure, both alike consisting of molecules, of cells, or
of fibres. Some decided, though not universal, differences exist in
chemical composition. Plants exhibit a decided predominance of ternary
compounds, or compounds which, like sugar, starch and cellulose, are
made up of the three elements, carbon, hydrogen and oxygen, but are,
comparatively speaking, poorly supplied with quaternary compounds, or
those which contain an additional element of nitrogen. Animals, on
the contrary, are rich in quaternary nitrogenized compounds, such as
albumen or fibrin. Still, in both kingdoms we find nitrogenized and
non-nitrogenized compounds, and it is only in the proportion which
these sustain to each other in the organism that animals differ in any
way from plants.
Before the invention of the microscope, no independent voluntary
movements, if we except the opening and closure of flowers, and their
turning towards the sun, the drooping of the leaves of sensitive plants
under irritation, and some other kindred phenomena, were known in
plants. Now, however, we know of many plants which are endowed, either
when young or throughout life, with the power of effecting voluntary
movements apparently as spontaneous and independent as those performed
by the lower animals, the movements being brought about by means of
little vibrating cilia, or hairs, with which a part or the whole of
the surface is furnished. When it is added that many animals are
permanently rooted, in their fully-grown condition, to solid objects,
it will at once be apparent that no absolute distinction can be made
between animals and plants merely because of the presence or absence of
independent locomotive power.
There is, however, a test, the most reliable of all that have been
discovered, by which an animal may be distinguished from a plant, and
that is the nature of the food and the products which are elaborated
therefrom in the body. Plants live upon such inorganic substances
as water, carbonic acid and ammonia, and they have the power of
manufacturing out of these true organic materials, and are therefore
the great producers of nature. All plants which contain green coloring
matter, technically called chlorophyll, break up carbonic acid in the
process of digestion into its two constituents of carbon and oxygen,
retaining the former and setting the latter free. And as the atmosphere
always contains carbonic acid in small quantities, the result is that
plants remove carbonic acid therefrom and give out oxygen. Animals, on
the other hand, have no power of living on water, carbonic acid and
ammonia, nor of converting these into the complex organic substances of
their bodies. That their existence may be maintained animals require to
be supplied with ready-made organic compounds, and for these they are
all dependent upon plants, either directly or indirectly. In requiring
as food complex organic bodies, which they ultimately reduce to very
simply inorganic ones, animals are thus found to differ from plants.
Whilst plants are the great manufacturers in nature, animals are the
great consumers. Another distinction, arising from the nature of their
food, is that animals absorb oxygen and throw out carbonic acid, their
reaction upon the atmosphere being exactly the reverse of that of
plants. There are organisms, it must be understood, which are genuine
plants so far as their nutritive processes are concerned, but which,
nevertheless, are in the possession of characters which could locate
them among the animals. Volvox, so abundant in our streams during the
proper seasons, affords a splendid illustration of the truth of this
statement. Plants, which are devoid of chlorophyll, as is the case with
the Fungi, do not possess the power of decomposing carbonic acid under
the influence of sunlight, but are like animals in requiring organic
compounds for their food. Two points must therefore be borne in mind
in regarding the general distinctions between plants and animals which
we have thus briefly outlined, and these are that they cannot often be
applied in practice to ambiguous microscopic organisms, and certainly
not to plant-forms that are destitute of chlorophyll.
That life should manifest itself certain conditions are essential,
but some of which, though generally present, are not absolutely
indispensable. One condition, however, seems to be very necessary, and
that is that the living body should be composed of a certain material.
This material, which forms the essential and fundamental parts of
everything living, whether vegetable or animal, is technically called
protoplasm. Other substances than it are often found in living bodies,
but it is in protoplasm only that vitality appears to be inherent.
But whether it is the same in plants as in animals is a matter of
opinion. One thing, however, seems reasonably certain, and that is that
it is the medium or vehicle through which vital force is made manifest.
Used in its general sense, protoplasm is chemically related in its
nature to albumen, and generally has the character of a jelly-like,
semi-fluid, transparent material, which, in itself, exhibits no
definiteness of structure. When heated to a certain temperature it
coagulates, just as the white of an egg does when boiled. Living
protoplasm has the power of movement, of increasing in size or of
maintaining its existence by the assimilation of fresh and foreign
materials, and of detaching portions of itself which may subsequently
develop into fresh masses. Though protoplasm be present in the ova of
animals and the seeds of plants, yet there is no external and visible
manifestation of life. There is in them what is called a dormant
vitality, which may remain for a long time unchanged, until altered
external circumstances cause the organism to pass into a state of
active life.
Generally, certain external conditions must be present before any
external vital phenomena can be manifested. The presence of atmospheric
air, or rather of free oxygen, is in an ordinary way essential to
active life. Life, that is its higher manifestations, is only possible
between certain ranges of temperature, varying from near the freezing
point to about 120° Fahrenheit. As water is a necessary constituent of
protoplasm in its living state, so it becomes an absolutely essential
requisite to the carrying on of vital processes of all kinds, for
the mere drying of an animal or plant will, in most cases, kill it
outright, and will always bring about a suspension of all visible
life-phenomena.
While the large majority of living beings are organized, or composed of
different parts, called organs, which sustain certain relations with
one another, and which discharge different offices, yet it must not
therefore be concluded that organization is a necessary accompaniment
of vitality, or that all living creatures are organized. Innumerous low
forms of life, so low that they occupy the very lowest place in the
scale of animated existences, absolutely exhibit no visible structure,
and cannot, therefore, be said to be organized, but they, nevertheless,
discharge all their vital functions just as well as though they
possessed special organs for the purpose. Concluding our theme, we
are forced to admit that animals are organized, or possess structure,
because they are alive, and not that they live because they are
organized. By carefully comparing the morphological and physiological
differences between different animals and plants, naturalists have
divided the entire animal and vegetable kingdoms into a number of
divisions, whose leading characteristics may be found in almost every
text-book. All that we promised ourselves when this work was first
thought of was a brief treatment of a few of the most interesting
life-forms of this planet of ours in the light of their ways and
doings, and the direction of human thought to those traits of character
and manifestations of conscious intelligence which fit them to become
partakers with man of that new life which awaits him beyond the grave.
PLANTS THAT FEED ON INSECTS.
Perhaps it would be difficult to find in the whole range of vegetable
creation anything more curious than the carnivorous or flesh-eating
plants. That animals eat plants creates in us no emotion of curiosity,
for this is the common law of nature. But that plants should devour
animals is a marvel to which few minds uninitiated in science would
give credence. Though these strange forms of vegetable life have been
known for about a century, yet it has been but a few years since the
attention of naturalists was first specially called to their habits
and character. No one has probably done more to explain the life and
operations of the flesh-eating plants than Mr. Darwin.
For centuries strange rumors had been circulated of the existence of
huge plants in the more remote and unvisited parts of Asia which would
imprison and destroy large animals and men that would venture within
reach of their great quivering leaves armed with hooked spines, the
flesh of the dead victim being absorbed into their structure, but all
these giant flesh-eating trees or plants have so far proved to be mere
myths. Science has discovered, however, that there is some foundation
for these exciting fictions, and it has not been obliged to go to
the distant East to find it, for flesh-eating plants are by no means
uncommon in this country and Europe. But these plants confine their
destructive propensities to the crawling and flying insects which
are beguiled by some tempting reward to rest on their leaves. Such a
strange provision of nature is no less interesting than if these plants
had the power to destroy the larger animals, for it is the fact itself
which startles the attention by its seeming reversal of natural laws.
No better example of carnivorous plants could be taken than _Dionæa
muscipula_, or to use the common name, Venus’s Fly-trap. It is a
species that is indigenous to North Carolina and the adjacent parts of
South Carolina, affecting sandy bogs in the pine forests from April
to June, and a representative of the _Droscraceæ_, or Sundew Family.
One cannot fail after once seeing it of becoming impressed with its
peculiar characteristics. It is a smooth perennial herb with tufted
radical leaves on broadly-winged, spatulate stems, the limb orbicular,
notched at both ends, and fringed on the margins with strong bristles.
From the centre of the rosette of leaves proceeds at the proper time
a scape or leafless stalk which terminates in an umbel-like cyme of
from eight to ten white bracted flowers, each flower being one inch
in diameter. The roots are small and consist of two branches each an
inch in length springing from a bulbous enlargement. Like an epiphytic
orchid, these plants can be grown in well-drained damp moss without any
soil, thus showing that the roots probably serve for the absorption
of water solely. Three minute pointed processes or filaments, placed
triangularly, project from the upper surface of each lobe of the
bi-lobed leaf, although cases are observed where four and even ten
filaments are found. These filaments are remarkable for their extreme
sensitiveness to touch, as shown not only by their own movement, but by
that of the lobes also. Sharp, rigid projections, diminutive spikes as
it were, stand out from the leaf-margins, each of which being entered
by a bundle of spiral vessels. They are so arranged that when the lobes
close they interlock like the teeth of an old-fashioned rat-trap. That
considerable strength may be had, the mid-rib of the leaf, on the lower
side, is quite largely developed.
Minute glands, of a reddish or purplish color, thickly cover the upper
surface of the leaf, excepting towards the margins, the rest of the
leaf being green. No glands are found upon the spikes or upon the
foliaceous footstalk. From twenty to thirty polygonal cells, filled
with purple fluid, constitute each gland. They are convex above,
somewhat flattened underneath, and stand on very short pedicels, into
which spiral vessels do not enter. They have the power of secretion
under certain influences, and also that of absorption. Minute octofid
projections, of a reddish-brown color, are scattered in considerable
numbers over the footstalk, the backs of the leaves and the spikes,
with a few on the upper surfaces of the lobes.
The sensitive filaments, which are a little more than one-twentieth
of an inch in length, and thin, delicate and tapering to a point, are
formed of several rows of elongated cells, filled with a purplish
fluid. They are sometimes bifid or even trifid at the apex, and towards
the base there is a constriction formed of broader cells, and beneath
the constriction an articulation, supported on an enlarged base,
consisting of differently shaped polygonal cells. As the filaments
project at right angles to the surface of the leaf, they would have
been in danger of being broken off whenever the lobes closed together
had it not been for the articulation, which allows them to bend flat
down. So exquisitely sensitive are these filaments, from their tips
to their bases, to a momentary touch, that it is hardly possible to
touch them even so lightly or quickly with any hard object without
causing the lobes to close, but a piece of delicate human hair, two and
a-half inches in length, held dangling over a filament so as to touch
it, or pinches of fine wheaten flour, dropped from a height, produce
no effect. Though not glandular, and hence incapable of secretion,
yet the filaments by their sensitiveness to a momentary touch, which
is followed by the rapid closure of the lobes of the leaf, assure to
Dionæa the necessary supply of insect food for all its wants.
Inorganic bodies, even of large size, such as bits of stone, glass
and such like, or organic bodies not containing nitrogeneous matter
in a soluble condition, as bits of cork, wood, moss for examples, or
bodies containing soluble nitrogeneous matter, if perfectly dry, such
as small pieces of meat, albumen, gelatine, etc., may be long left on
the lobes, and no movement is excited. But when nitrogeneous organic
bodies, which are all damp, are left on the lobes, the result is widely
different, for these then close by a slow and gradual movement and not
in a rapid manner as when one of the sensitive filaments is touched
by a hard substance. Small purplish, almost sessile glands, as has
already been stated, thickly cover the upper surface of the lobes.
These have the power both of secretion and absorption, but they do not
secrete until excited by the absorption of nitrogeneous matter. No
other excitement, as far as experiments show, produces this effect.
When the lobes are made to close over a bit of meat or an insect, the
glands over the entire surface of the leaf emit a copious discharge, as
in this case the glands on both sides are pressed against the meat or
insect, the secretion being twice as great as when the one or the other
is laid on the surface of a single lobe; and as the two lobes come
into almost close contact the secretion, containing dissolved animal
matter, diffuses itself by capillary attraction, causing fresh glands
on both sides to begin secreting in a continually widening circle. The
secretion is almost colorless, slightly mucilaginous, moderately acid,
and so copious at times in the furrow over the mid-rib as to trickle
down to the earth. But all this secretion is for the purposes of
digestion. Be the animal matter which the enclosed object yields ever
so little, it serves as a peptogene, and the glands on the surface of
the leaf pour forth their acid discharge, which acts like the gastric
juice of animals.
[Illustration: VENUS’S FLY-TRAP.
How It Captures Insects.]
Now as to the manner in which insects are caught by the leaves of
_Dionæa muscipula_. In its native country they are caught in large
numbers, but whether they are attracted in any special way no one
seems to know. Both lobes close with astonishing quickness as soon
as a filament is touched, and as they stand at less than a right
angle to each other, they have an excellent chance of capturing any
intruder. The chief seat of the movement is near the mid-rib, but is
not restricted to this part. Each lobe, when the lobes come together,
curves inwards across its whole breadth, the marginal spikes alone not
becoming curved. From the curving inwards of the two lobes, as they
advance towards each other, the straight marginal spikes intercross
by their apices at first, and ultimately by their bases. The leaf is
then completely shut and encloses a shallow cavity. If made to shut
merely by the touching of one of the sensitive filaments, or by the
inclusion of an object not yielding soluble nitrogeneous matter, the
two lobes retain their inwardly concave form until they re-expand. The
re-expansion, when no organic matter is enclosed, varies according
to circumstances, a leaf in one instance being fully re-expanded in
thirty-two hours.
But the lobes, when soluble nitrogeneous matter is included, instead
of remaining concave, thus containing within a concavity, slowly press
closely together throughout their entire breadth, and as this takes
place the margins gradually become a little everted, so that the
spikes, which at first intercrossed, at last project in two parallel
rows. So firmly do they become pressed together that, if any large
insect has been caught, a corresponding projection is clearly visible
on the outside of the leaf. When the two lobes are thus completely
closed, they resist being opened, as by a thin wedge driven with
astonishing force between them, and are generally ruptured rather than
yield. If not ruptured, they close again with quite a loud flap. The
slow movement spoken of, excited by the absorption of diffused animal
matter, suffices for its final purpose, whilst the movement brought on
by the touching of one of the sensitive filaments is rapid, and thus
indispensable for the capturing of insects.
Leaves remain shut for a longer time over insects, especially if the
latter are large, than over meat. In many instances where they have
remained for a long period over insects naturally caught, they were
more or less torpid when they reopened, and generally so much so during
many succeeding days that no excitement of the filaments caused the
least movement. Vigorous leaves will sometimes devour prey several
times, but ordinarily twice, or, quite often, once is enough to render
them unserviceable.
What purpose the marginal spikes, which form so conspicuous a feature
in the appearance of the plant, subserve was unknown until the genius
of Darwin solved the mystery. It was he that showed that elongated
spaces between the spikes, varying from one-fifteenth to one-tenth of
an inch in breadth according to the size of the leaf, are left open
for a short time before the edges of the lobes come into contact,
consequent upon the intercrossing of the tips of the marginal spikes
first, thus enabling an insect whose body is not thicker than these
measurements to escape, when disturbed by the closing lobes and
the increasing darkness, quite easily between the crossed spikes.
Moderately sized insects, if they try to escape between the bars, will
be pushed back into the horrid prison with the slowly closing walls,
for the spikes continue to close more and more until the lobes are
brought into contact. Very strong insects, however, manage to effect
their release. It would manifestly be a great disadvantage to the
plant to remain many days clasped over a minute insect, and as many
additional days or weeks in recovering its sensibility, inasmuch as
a very small insect would afford but little nourishment. Far better
would it be for the plant to wait until a moderately large insect was
captured, and to allow the little ones to escape, and this advantage is
gained by the slow intercrossing of the marginal spikes, which, acting
like the large meshes of a fishing-net, allow the small and worthless
fry to pass through.
Touching any one of the six filaments is sufficient to cause both
lobes to close, these becoming at the instant incurved throughout
their entire breadth. The stimulus must therefore radiate in all
directions from any one filament, and it must also be transmitted with
considerable rapidity across the leaf, for in all ordinary cases,
as far as the eye can judge, both lobes close at the same time.
Physiologists generally believe that in irritable plants the excitement
is transmitted along, or in close connection with, the fibro-vascular
bundles. Those in Dionæa seem at first sight to favor this belief, for
they run up the mid-rib in a great bundle, sending off small bundles
almost at right angles on each side, which bifurcate occasionally as
they stretch towards the margin, the marginal branches from adjoining
branches uniting and entering the marginal spikes. Thus a continuous
zigzag line of vessels runs round the whole circumference of the
leaf, while in the mid-rib all the vessels are in close contiguity,
so that all parts of the leaf seem to be brought into some degree of
communication. The presence of vessels, however, is not necessary for
the transmission of the motor impulse, for it is transmitted from the
apices of the sensitive filaments, which are hardly one-tenth of an
inch in length, into which no vessels are seen to enter. Slits made
close to the bases of the filaments, parallel to the mid-rib, and thus
directly across the course of the vessels, sometimes on the inner
and sometimes on the outer sides of the filaments, do not interfere
with the transmission of the motor impulse along the vessels, and
conclusively show that there is no necessity for a direct line of
communication from the filament, which is touched towards the mid-rib
and opposite lobe, or towards the outer parts of the same lobe.
With respect to the movement of the leaves, the wonderful discovery
made by Dr. Burdon Sanderson, and published in 1874, offers an easy
explanation. There is, says this distinguished authority, a normal
electrical current in the blade and footstalk, which, when the leaves
are irritated, is disturbed in the same manner as is the muscle of an
animal when contraction takes place.
After contraction has endured for a greater or less time, dependent
upon circumstances which we do not well understand, re-expansion of
the leaves is effected at an insensibly slow rate, whether or not any
object is enclosed, both lobes opening in all ordinary cases at the
same time, although each lobe may act to a certain extent independently
of the other. The re-expansion is not determined by the sensitive
filaments, for these may be cut off close to their bases, or be
entirely removed, and re-expansion occur in the usual manner. It is
believed that the several layers of cells forming the lower surface of
the leaf are always in a state of tension, and that it is owing to this
mechanical state, aided probably by fresh fluid being drawn into the
cells, that the lobes begin to separate as soon as the contraction of
the upper surface diminishes.
Six known genera, Drosophyllum, Roridula, Byblis, Drosera, Dionæa and
Aldrovanda comprise the Droseraceæ, all of which capture insects. The
first three genera effect this purpose solely by the viscid fluid
secreted from their glands, and the last, like Dionæa, which has
already been described, through the closing of the blades of the leaf.
In these last two genera rapid movement makes up for the loss of viscid
secretion. But of all the genera none is more interesting than the
typical Sundews.
Growing in poor peaty soil, and sometimes along the borders of ponds
where nothing else can grow, certain low herbaceous plants, called
Droseras, abound. So small and apparently insignificant are they,
that to the ordinary observer they are almost unnoticed. But they
have peculiarities of structure and nature that readily distinguish
them. Scattered thickly over their leaves are reddish bristles or
tentacles, each surmounted by a gland, from which an extremely viscid
fluid, sparkling in the sunlight like dew, exudes in transparent
drops. Hence the common name of Sundew by which the half-dozen species
found in the United States east of the Mississippi River are known. A
one-sided raceme, whose flowers open only when the sun shines, crowns
a smooth scape, which is devoid of tentacles. _Drosera rotundifolia_,
our commonest species, has a wide range, being indigenous to both
Europe and America. In the United States it extends from New England
to Florida and westward, and is occasionally associated with
_Drosera longifolia_, a form with long strap-shaped leaves, but
whose distribution is mostly restricted to maritime regions, from
Massachusetts to Florida.
[Illustration: ROUND-LEAVED SUNDEW.
Leaves Acting as Stomachs.]
All of the species are remarkably similar in habits, capturing insects,
and digesting and absorbing the soft parts, a circumstance which
explains how these plants can flourish in an extremely poor soil where
mosses, which depend almost entirely upon the atmosphere for their
nourishment, only can live. Although the leaves of the Droseras at
a hasty glance do not appear green, owing to the purple color of the
tentacles, yet the superior and inferior surfaces of the blade, the
stalks of the central tentacles, and the petioles contain chlorophyll,
rendering the best of evidence that the plants obtain and assimilate
carbon dioxide from the air. But when the poverty of the soil where
these plants grow is considered, it is at once apparent that their
supply of nitrogen would be exceedingly small, or quite deficient,
unless they had the power of obtaining it from some other source. From
captured insects this important element is largely obtained, and thus
we are prepared to understand how it is that their roots, which consist
of only two or three slightly divided branches, from one-half to one
inch in length, and furnished with absorbent hairs, are so poorly
developed. From what has been stated it would seem that the roots but
serve to imbibe water, but there is no doubt that nutritious matters
would also be absorbed were they present in the soil.
With the edges of its leaves curled so as to form a temporary stomach,
and with the glands of its closely-inflected tentacles pouring forth
their truly acid secretion, which dissolves animal matters that are
subsequently absorbed, Drosera may be said to feed like an animal. But,
unlike an animal, it drinks by means of its roots, and largely, too,
for it would not be able to supply its glands with the necessary viscid
fluid. The amount needed is by no means an inconsiderable quantity, as
two hundred and seventy drops may sometimes be exposed during a whole
day to a glaring sun. Such a profuse exudation implies preparations for
hosts of insect visitors. In this Drosera has not miscalculated. Its
bright pink blossoms and brilliant, glistening dew lure vast numbers of
the smaller kinds, and the larger ones, too, to certain death. But the
wholesale destruction of life that goes on is much in excess of what
the plant requires for food. While the smaller flies remain adherent
to the leaves, affording them the needed aliment, the larger insects,
after death, fall around the roots, where they decay and fertilize
the soil with nitrogen, which doubtless through the proper channels
makes its way into the body of the plant, thus helping to give it
tone and vigor. There are times when these plants work better than at
others, but whether this is caused by the electrical condition of the
atmosphere, or the amount of its contained moisture, is a question
which science has not positively determined.
_Drosera longifolia_ folds it leaves entirely around its victim, from
the apex down to the petiole after the manner of its vernation, but
in _Drosera rotundifolia_, whose marginal tentacles are longer, the
tentacles simply curve around the object, the glands touching the
substance, like so many mouths receiving nourishment. Experimented
upon with raw beef, the tentacles of healthy leaves, from within to
without, but in periods of time varying from six to eight or nine
hours, clasp firmly the beef, almost concealing it from view. Equally
vigorous leaves, however, made no move towards clasping a bit of dry
chalk, a chip of flint, or a lump of earth. Bits of raw apple cause
a curving of the tentacles, but very few of the glands are seen
touching them. It would seem, therefore, that these plants are really
carnivorous, preferring animal substances, which they, by the aid of
some ferment analogous to pepsin, which is secreted by the glands, are
able to absorb. A minute quantity of already soluble animal matter is
the exciting cause, and this must be taken in by the glands, or there
is no secretion of the fermenting material.