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GEORGE FRANCIS ATKINSON
BOTANICAL LIBRARY
1920

CUDNEY TAD UT
3 1924 031 496 734

_ Olin,anx

Cornell University

Library

The original of this book is in
the Cornell University Library.

There are no known copyright restrictions in
the United States on the use of the text.

http://www. archive.org/details/cu31924031496734

OUNG Poort

Botany for Voung People.

PART II.

HOW PLANTS BEHAVE:

HOW THEY MOVE, CLIMB, EMPLOY INSECTS
TO WORK FOR THEM, &c.

By ASA GRAY.

IVISON, BLAKEMAN & COMPANY,
PUBLISHERS,

NEW YORK AND CHICAGO.

i]

AS61612

Entered according to Act of Congress, in the year 1872,

BY ASA GRAY,

in the Office of the Librarian of Congress, at Washington.

PREFACE.

—_—_—_—

HOW PLANTS GROW, the first part of Borany ror Youne Psorpte AND
Common ScHooLs, was written fourteen years ago, in the endeavor to provide a
book upon Elementary Botany, adapted to the instruction of young people, even
of children, yet truly presenting, albeit in a simple way, the leading facts, methods,
and principles of the science as understood by its masters. The book has been
successful. It will probably enable a young person, under the guidance of a quali-
fied teacher, to obtain a larger, truer, and worthier knowledge of Botany than
many grown people could readily find the way to acquire a generation ago.

That young people, that all students, indeed, should be taught to observe, and
should study Nature at sight, is a trite remark of the day. But it is only when
they are using the mind’s eye as well, and raising their conceptions to the rela-
tions and adaptations of things, that they are either learning science or receiv-
ing the full educational benefit of such a study as Botany or any other depart-
ment of Natural History.

There is a study of plants and flowers admirably adapted, while exciting a
lively curiosity, to stimulate both observation and thought, to which I have
long wished to introduce pupils of an early age. The time has now arrived
in which I may make the attempt, and may ask young people to consider not
only ‘How Plants Grow,’ but How Plants Act, in certain important respects,
easy to be observed, — everywhere open to observation, but (like other common
things and common doings) very seldom seen or attended to. This little trea-
tise, designed to open the way for the young student into this new, and, I trust,

viii PREFACE.

attractive field, may be regarded as a supplement to the now well-known book,
the title of which is cited at the beginning of this prefatory note. If my expec-
tations are fulfilled, it will add some very interesting chapters to the popular
history of Plant-life.

Although written with a view to elementary instruction, and therefore with all
practicable plainness, the subjects here presented are likely to be as novel, and
perhaps as interesting, to older as to young readers.

To those who may wish to pursue such studies further, and to those who will
notice how much is cut short or omitted (as, for instance, all reference to dis-
coverers and to sources of information), I may state that I expect to treat this
subject in a different way, and probably with somewhat of scientific and historical
fulness, in a new edition of a work intended for advanced students.

AG.

Botanic Garpen, Harvarp UNIVERSITY,
February 20, 1872.

Vignette Title-Page.— Left-hand side, an Ivy climbs by rootlets and « Passion-flower
by tendrils; right-hand, a Nepenthes by pitcher-bearing tendrils, and a Morning-Glory by
twining stem : bottom, at the left of the centre, a Rhodochiton, and at the right a Maurandia
climb by their leafstalks. Bottom, left-hand side, a Green Orchis (Habenaria orbiculata) sends
up from between a pair of large round leaves a raceme of long-spurred flowers. Two Orchid
Air-plants at the top, viz., Stanhopea tigrina at the centre, a Phalenopsis at the right-hand
corner. Two leaves of Sarracenia rubra, an American Pitcher-plant, rise from near the lower
vight-hand corner : in front of them is a Sundew, Drosera rotundifolia ; at the centre a Venus's
¥)y-trap, Dionea muscipula.

HOW PLANTS BEHAVE.

CHAPTER L,

HOW PLANTS MOVE, CLIMB, AND TAKE POSITIONS.

1. Two plants — one of them common in cultivation, and the other rarer, but
almost as easy to raise —are looked upon as vegetable wonders, namely, the
Sensitive Plant and Desmodium gyrans. They are striking examples of

2. Plants that move their Leaves freely and rapidly. In the well-known Sensitive
Plant (Mimosa pudica) the foliage quickly changes its position when touched,
appearing to shrink away from the hand. Fig. 1 represents
a piece of stem with two (compound) leaves; the lower one
expanded, as it is in sunshine and when untouched: the
upper leaf shows the position which is taken, by quick move-
ments, when roughly brushed by the hand. It makes three
movements. First, the numerous leaflets close in pairs,
bringing their upper faces together and also inclining for-
wards; then the four branches of the leafstalk, which were
outspread like the rays of a fan, approach each other; at
the same time the main leafstalk
turns downward, bending at its joint
with the stem. So the leaf (for it is
all one compound leaf) closes and
seemingly collapses at the touch.
In a short time, if left to itself,
it slowly recovers the former out-
spreading position.

3. The second plant, Desmodium Fig. 1. Sensitive Plant.
gyrans (we have no common name for it), also belongs to the great Pulse Family,
and flourishes in warm climates. It inhabits the warmer parts of India, but is

10 HOW PLANTS MOVE, CLIMB,

easy to cultivate in a hot-house, or even in an open garden during the heat of
summer. The leaves are of only three leaflets (Fig. 2), a large one at the end
of the leafstalk, accompanied by a pair of small leaflets, one on each side. The
end leaflet usually moves too slowly to be
seen, and only as light is given or withdrawn ;
we have seen it move rather briskly, however,
upon one occasion. The side leaflets are
active enough. Under the temperature of a
sultry summer’s day they may be seen to rise
and fall by a succession of jerking move-
ments, not unlike those of the second-hand
of a clock, but without much regularity, now
stopping for some time, then moving briskly,
always resting for a while in some part of
their course, commonly at the highest and
lowest points, and starting again without ap-
parent cause, seemingly of their own will.
The movement is not simply up and down,
but the end of the moving leaflet sweeps
more or less of a circuit. It is not set in
motion by a touch, but begins, goes on, or
stops of itself.

4, Whether these movements are of any
use to these plants is more than we can tell ;

Fig. 2. Desmodium gyrans. nor do we very well know how they are ef-
fected. The attempts that have been made to explain how the motion is brought
about need not be considered here. However done, it is clear that the leaves
_move by their own act, in the one case responding to a touch; in the other
independently, or, as we say, spontaneously.

5. Now, truly wonderful as these two plants are, there is nothing really pecu-
liar about them. By which is meant, not merely that some other plants are
known to move as freely, though perhaps less rapidly, but that many ordinary
plants perform similar movements, in one or both of these ways, and that all
plants possess similar faculties. The hour-hand of the clock moves as really as
the minute-hand and the second-hand, although the motion of the latter only is

AND TAKE POSITIONS. 11

discerned by the eye. Lifeless things may be moved or acted on; living beings
move and act, — plants less conspicuously, but no less really, than animals. In
sharing the mysterious gift of life, they share some of its simpler powers.

6. The Sleep of Plants, as Linneeus fancifully termed it, — that. is, the different
position which leaves and leaflets take at nightfall, is a familiar case of free
movement, only the motion is too slow to be seen by the eye. The Sensitive
Plant is a good instance of this. Its leaves slowly assume the same posture at
or before sunset that they rapidly do when disturbed by a touch or jar, and they
remain so until the light of morning. Most other plants of the Pulse Family
(the Locusts, for instance), and many of other families, take a very different posi-
tion by night from that of day. The end-leaflet of Desmodium gyrans hangs
down as soon as the light of day begins to wane, but rises and turns its upper
face to the sun again in the morning.

7. The Turning of Green Shoots to the Light, which we observe when house-plants
are kept in our windows, and the turning of the upper face of most leaves
towards the lighted side, are similar cases of slow movement or bending. Many
people suppose that the green shoot grows towards the light, whereas it only bends
towards it. One has only to notice the behavior of the slender stemlet of a seed-
ling Radish, or of any similar plant, when set in a window, and see it bending
towards the lighted side in a few minutes, before it has had time to grow percep-
tibly, to be convinced that the growth and the bending are different acts.

8. The contrary Directions of Stem and Root when springing from the seed are of
this kind. Read the brief account given in ‘How Plants Grow,’ paragraphs 28
and 29, and watch the operation in young seedlings. Note how one end of the
embryo plantlet rises out of the soil and into the light, and, if need be, turns
quite round to do so, while the other turns from the light and strikes deeper into
the ground. This shows that it is the plant itself which acts in taking these direc-
tions, and that these positions are the result of real movements, however slow.

9. Climbing Plants afford some of the most curious and most varied illustrations
of the movements which plants perform; and in these it is easy to see what
the movements are for. The advantage which a plant gains by climbing is, that
it may thereby rise higher and get a fuller exposure to the light than it could
with the same amount of material if it stood independently. Compare the
amount of wood or other material in a tree with that of any climber which has
ascended it and made a support of its topmost branches. Plants climb in
several ways. Some are

12 HOW PLANTS CLIMB.

10. Root-Climbers. ‘These creep up the face of rocks or walls, or the trunks of
trees, their stems, as they grow, pressing against the support and adhering to it by
means of numerous rootlets which they throw out: the end of these rootlets com-
monly flattens out or expands into a small disk or holdfast which adheres to the
wall or bark, etc. Ivy, that is, true or ‘“‘ English” Ivy, is a good example of this.
See the vignette title-page, left-hand side. Our Poison Ivy and the Trumpet
Creeper climb in the same way. There is, perhaps, no more effectual mode of
climbing when bare walls or large trunks are the support. In other cases

11. Twiners, i. e. Twining Plants, have an obvious advantage. To twine spi-
rally round some supporting body is 2 common mode of climbing. This is
done by a
y movement
# ofthestem
itself, not

- less re
markable in reality than that of the leaflets of the Desmo-
dium gyrans, just described, and indeed of similar nature.
The Hop and some Honeysuckles twine with the sun.
Morning Glory, and all the Bindweeds of the Convolvulus
Family, Beans, and indeed most of the common twiners,
turn against the sun, that is, from the left to the right
hand of the observer.

12. When a twining stem overtops its support, the
lengthening shoot is seen thrown over to one side, and
usually outstretched, as in Fig. 3. One might suppose it
had fallen over by its weight; but it is not generally so.
If turned over, say to the north, when first observed, it will
probably be found reclining to the south an hour or so
later, and an hour later again turned northward. That is,
the end of the stem is sweeping round in a circle continu-

fi ally, like the hand of a clock. It keeps on growing as it
Fig. 8. Morning Glory, twining. revolves; but the revolving has nothing to do with the
growth, and, indeed, is often so rapid that several complete sweeps may be made
before any increase in length could be observed. The time of revolving varies in
different species, It also depends upon the weather, being slow or imperceptible

HOW PLANTS CLIMB. 13

when it is cool, and more rapid when it is warmer. Sometimes it stops when
everything seems favorable, and starts again after a while. The Hop, Bean, and
Morning Glory are as quick as any. In a sultry day, and when in full vigor, they
commonly sweep round the circle in less than two hours. They move by night
as well as by day. When the free summit of a twining stem is outstretched to
two feet or more in length, so as to magnify the motion, this is sometimes rapid
enough to be actually seen in some part of the circuit. :

13. Because twining stems are often twisted more or less, some have supposed
that the twisting was the cause of the revolving sweep of the free end. If so, the
stem below would in a day or two be likely to twist itself off. And twiners sel-
dom twist much when climbing a smooth and even support. To learn how the
sweeps are made, one has only to mark a line of dots along the upper side of the
outstretched revolving end of such a stem (say that of the Morning Glory, Fig. 3),
and to note that when it has moved round a quarter of a circle, these dots will be
on one side; when half round, the dots occupy the lower side ; and when the revo-
lution is completed, they are again on the upper side. That is, the stem revolves
by bowing itself over to one side, — is either pulled over or pushed over, or both,
by some internal force, which acts in turn all round the stem in the direction in
which it sweeps; and so the stem makes its circuits without twisting.

14. So the sweeping round of the stem is a movement like that wonderful one
of the leaflets of Desmodium gyrans, just described, only slower. And here we
see what it is for. The sweeping movement of the stem is the cause of the twin-
ing. The stem sweeps round that it may reach some neighboring support ; as it
grows it sweeps a wider and wider space, that is, reaches farther and farther out.
When it strikes against any solid body, like the stalk of a neighboring plant, it is
stopped : but the portion beyond the contact is free to move as before; and, con-
tinuing to lengthen and to move on, it necessarily winds itself round the support,
that is, cwines. This is the explanation of twining climbers.

15. Leaf-Climbers. Some plants climb by their leaves, either the blade, or more
commonly the petiole, hooking or coiling round something within reach. Clema-
tis or Virgin’s-Bower is a familiar instance. In all the common species of Clema-
tis the leaves are compound, and the divisions of the petiole, or at first the young
leaflets themselves, bend round the stalks or branches of neighboring plants, or
any supporting object not too large to be grasped, and so ascend. Lophospermum
and Maurandia (handsome flowering herbs of the gardens), and one or two other

14 HOW PLANTS CLIMB.

plants of the same family, with simple leaves, climb freely in this way, neatly
coiling their leafstalk round any slender support within reach. The vignette
title-page shows two illustrations of this, in the lower part.

16. A rather common cultivated species of
Nightshade, Solanum jasminoides, is a good ex-
ample of the same kind, and furnishes the
present illustration, in Fig. 4. It is interesting
to notice how the leafstalks of this plant which
y have clasped a support grow much stouter and
firmer than those which have not, becoming
three or four times as thick as before, —as if
the need of greater strength and rigidity some-
how brought it about.

17. A leaf-climber has this advantage over a
twiner, that it may reach a given height with
less amount of substance. Its stem may rise
straight up, and save much in length over the
twiner, which has to produce twice or thrice that
length of stem in reaching the same elevation, on
i account of the coils.

Fig. 4. Sol janine ,elimbing by 18. To understand how leaves or leafstalks lay

Atsilentstalics: hold of a support, we must refer back to the Sen- ~
sitive Plant (Paragraph 2); its leaves and leafstalks, we know, respond to the
touch of a foreign body by a movement. So do those of leaf-climbers: only the
movement by which they clasp the support is very slow and incited only by pro-
longed contact. If one of these leafstalks be rubbed for some time with a piece
of wood, it will generally respond to the irritation by curving ; but it will be two
or three days about it; and in two or three days more it may straighten itself,
unless the stick is left in contact with the leafstalk: then it will clasp it perma-
nently, making one or perhaps two turns around it, and in time it may thicken
and harden. That the climbing in such cases is the result of a movement, how-
ever slow, under sensitiveness to touch, is further shown by the behavior of
tendrils.

19. Between leaf-climbing and tendril-climbing there is every gradation. In
Gloriosa, a tropical plant of the Lily Family, the tip of a simple leaf extends

HOW PLANTS CLIMB. 15

into a slender hook, for laying hold of anything within reach. In Mepenthes (a
climbing sort of Pitcher-plant, shown on the right-hand side of the mee title,
and one leaf in Fig. 5, on a larger scale), the tip of the
blade grows out into a tendril which acts just as does the
leafstalk of Fig. 4 and of the other leaf-climbers ; at the
end of this a pitcher, with a lid to it, is generally formed.
Of this more is to be said hereafter. In that vigorous
climber, Cobea, the branching claws and grapples which
are used to such effect are merely the upper portion of
a compound leaf changing into tendrils. The tendrils of
a Pea are similar, but simpler.

20. Tendril-Climbers are best illustrated by such plants
as Passion-flowers (see vignette title, on the left, and Fig.
6): here the tendril is a simple thread-like shoot, for the
purpose of climbing and nothing else. This is the most
exquisite, and under many circumstances the most advan-
tageous, as it is one of the commonest of the contrivances
for climbing. The tendril, as it grows, stretches out
horizontally, as if in search of a supporting object. More slender than a stem
or any other sort of stalk, it can thus extend farther at the least expense of
material.

21. In the most perfect tendrils, and notably in the slender Passion-flowers
(such as the annual Passiflora gracilis, and the Maple-leaved species, P. acertfolia,
Fig. 6), opportunities for securing a hold are much increased by the revolving of
the tendril. It sweeps circuits, like the stem of a twiner, although with less reg-
ularity, sometimes, however, with greater rapidity. In hot weather these tendrils
often move through the complete circle in an hour or less, or even so fast that
the motion of the end of a long tendril may sometimes be distinctly seen in a
part of its course. The revolving of tendrils is more fitful than that of twining
stems: they often stop for a while, or move very slowly or irregularly. Some
tendrils, as we shall soon see, do not revolve at all.

22. If a tendril does not reach anything, after attaining its full growth and
remaining for some time outstretched, it then either coils up from the end (as
seen in the middle tendril of Fig. 6), or else becomes flabby, hangs down in an
exhausted state, dies, and withers away.

Fig. 5. Leaf of Nepenthes.

16 HOW PLANTS CLIMB.

23. When, however, the fresh and active
tendril comes in contact with a neighboring
stalk, or any similar support, it hooks or coils
its end round it; then, having secured a hold,
it shortens by coiling up its whole length, or a
good part of it. This commonly draws up the
climbing stem nearer to its support, and makes
it easier for the younger tendrils above to gain
their hold. A tendril which has taken hold
and coiled up usually becomes stouter, rigid,
and much stronger than it was before. One
which would break with an ounce weight be-
comes capable of supporting two or three
pounds.
24. There is a difference to be noticed be-
tween the coiling of a free tendril and of one
which has taken hold. It is plainly shown in
Fig. 6. The loose tendril coils up, if at all,
from the end, and in a simple spiral or curl.
But when attached to a support, both ends be-
ing fixed, it cannot coil in this way. It has to
coil in the middle ; and the coiling of one part,
say from right to left, requires another part to
Fig. 6. Maple-leaved Passion-flower, with ten- twist as much in the opposite direction. So
as aaa the coil has a break in the middle, half twist-
ing one way and half the other way, as is shown in the lower tendril of the figure.
A longer tendril often has three or four, or even five or six, such breaks, the por-
tions coiled successively in opposite directions.

25. Pumpkins, Squashes, and all the Gourd Family furnish excellent examples
of these actions of tendrils. Their tendrils are like those of Passion-flowers, ex-
cept that they are mostly branched or compound, and, like the claws of a bird,

. stretch out in several directions.

HOW PLANTS CLIMB. 17

26. There is great variety in the behavior of different tendrils. Those of the
Grapevine do not make sweeps, but stretch out away from the light, or in the
direction from which least light comes, —an instinct which is apt to lead them
to a support, — and the two forks diverge, as if feeling for something to lay hold
of. When they reach anything that can be surrounded, one fork commonly grasps
from one side, the other from the opposite side, somewhat as an object would be

. grasped by a thumb and finger.

27. The more branching tendrils of the Virginia Creeper equally turn from the
light, and therefore towards the wall or trunk, which this climber delights to
occupy and cover.
When their tips
reach the wall they
expand into a disk
or flat plate, which
adheres firmly to
the surface. This
particularly adapts
the Virginia Creeper \
to ascending walls
or other flat sur-
faces. The tendrils

which do not attach

themselves remain Fig. 7- Virginia Creeper: tendril beginning to form its disks or holdfasts. 8. Older
branches with full-formed disks.

slender, and in a
week or two shrink and wither away. Those that do usually spread their branches
widely apart, like fingers of an outstretched hand, form their disks and fix them
fast to the wall; then they contract more or less into coils, and at length grow
stronger and more rigid; so that they last for years, and endure a pretty heavy
strain without breaking or parting from the wall. It is most interesting to see
how the strain is divided by these five or six separate attachments, by the coiling
of each branch to give elasticity, so that the pull shall come upon all at once, and
to note the strengthening of the whole by the formation of more woody fibre.
The strain is distributed among the branches, and the whole combination is so
strong that it is rarely torn away by wind or storm.

28. In revolving tendrils the most wonderful thing to remark is the way in

2

18 HOW PLANTS CLIMB.

which they avoid winding themselves around the stem they belong to. The ac-
tive tendrils are of course near the top of the stem or branch. The growing
summit beyond the tendril now seeking a support is often turned over to one side,
so that the tendril, revolving almost horizontally, has a clear sweep above it. But
as the growing stem lengthens and rises, the tendril might strike against it and be
wound up around it. It never does. If we watch these slender Passion-flowers,
which show the revolving so well in a sultry day, we may see, with wonder, that
when a tendril, sweeping horizontally, comes round so that its base nears the
parent stem rising above it, it stops short, rises stifly upright, moves on in this
position until it passes by the stem, then rapidly comes down again to the horizon-
tal position, and moves on so until it again approaches and again avoids the
impending obstacle !

29, Other equally curious illustrations might be given; but these may serve
the purpose of opening the eyes to what is going on around us, awaken an intel-
ligent interest, and excite to further observation. They are enough to make it
clear that the two vegetable prodigies described at the beginning of this chapter,
‘surprising as they are, have no peculiar endowments. Climbing plants generally,
and tendril-climbers especially, exhibit both the free movements of the one, and
the movement in response to external irritation of the other. The sweeping round
-of tendrils is like the movement of the leaflets of Desmodium gyrans: their coil-
ing upon contact, and the similar coiling of some leafstalks, are to be compared
with the movement of the leaflets and leafstalks of the Sensitive Plant.

30. This becomes evident when the motion is quick enough to be seen by the
eye. It has already been stated that a very long tendril of one of the slender
‘Passion-flowers has often been seen to move. Still oftener may it be seen to coil
up at the tip when gently rubbed. This is also to be seen in the Bur-Cucumber
(Steyos), a common weed of the Gourd Family. When, in a sultry summer day,
we gently rub, with a stick or with the finger, the upper end of a vigorous tendril,
it will respond within half a minute by coiling up so rapidly that the motion may
be distinctly seen. It will soon straighten, but will coil again if the rubbing is
repeated. If a stick be left in contact the coiling will be permanent; and a
downward propagation of the same action is what throws the whole tendril into
spiral coils.

WHY FLOWERS ENTICE INSECTS TO VISIT THEM. 19

CHAPTER II.

HOW PLANTS EMPLOY INSECTS TO WORK FOR THEM.

31. Puants supply animals with food. That, we may say, is what they were
made for. In some cases the whole herbage, in others the fruit, seeds, bulbs,
tubers, or roots, are fed upon. But vast numbers of insects, and some birds
(such as humming-birds), draw nourishment from plants, mainly from their flow-
ers, without destroying or harming them. By their colors, odors, and nectar,
blossoms attract insects in great numbers and variety.

32. Nectar, the sweet liquid which most flowers produce, is the real attraction :
bright colors and fragrance are merely advertisements. This sweet liquid is often
called honey ; but nectar is the proper name for it, as it is not really honey until
it is made so by the bee. Some insects also take pollen (the powdery matter pro-
duced in the anthers: see How Plants Grow, paragraph 17), either for their own
consumption or that of their progeny. That may possibly do the plant some
harm. But the nectar they consume is of no use to flowers that we know of,
except it be to entice insects.

33. So flowers are evidently useful to insects, and most flowers are feeding-
places for them. Where free Innches are provided some advantage is generally
expected from the treat: and we are naturally led to inquire,

34. Why should Flowers entice Insects to visit them? What advantage are they
likely to derive in return for the food they offer? In certain cases the use of in-
sects to flowers is evident enough. When, in early spring, we see Willow-catkins
thronged with honey-bees, and notice that their blossoms are of the separated
sort (How Plants Grow, 205), — those of one tree consisting of stamens only, of
another tree, of pistils only, — and that the bees flying from tree to tree have their
bodies well dusted with pollen, we may conclude that the bees are doing useful
work in carrying pollen from the stamen-bearing flowers that produce it to the
pistil-bearing flowers that require it in order to set seed (see How Plants Grow,
16, 196). While feeding from the stamen-bearing catkins, their heads and bodies,
rubbing against the anthers, get dusted with the pollen. When they fly to a

20 HOW PLANTS EMPLOY INSECTS TO WORK FOR THEM.

tree with pistil-bearing catkins, some of this pollen is rubbed upon the stigmas,
and in consequence its fruit may set and the seeds be perfected. The stamens and
pistils of Willows being on different trees, and the two sorts of trees very likely
at a wide distance apart, it is necessary that the pollen should be carried by insects
or some other conveyance, if the Willow is to be propagated by seed.

35. It might have been left to the winds to waft the pollen. It is so in Pine-
trees, Spruces, and the like. But considering what enormous superabundance of
pollen these trees produce (even when the two sorts of flowers are on the same
tree) in order to make sure of the result, one cannot doubt that there is great
economy in the arrangement by which the busy bees are called upon to do the carry-
ing. In such instances the insects are probably as useful to the flowers as the
flowers are to the insects.

36. Why should perfect Flowers need to attract Insects? Far the larger number of

flowers are perfect, that is, are furnished with both stamens and pistils: the sta-
mens are almost always more numerous than the pistils, and encompass them ;
.and each anther contains a thousand or many thousand times more grains of pol-
len than there are of seeds to be fertilized, and all so near or in such position
that it appears as if the pollen, or a sufficient quantity of it for the purpose,
must needs be shed upon the stigmas, either with or without the aid of the wind.
Yet here insects, in searching the blossoms for food, might be helpful even if not
needful.

37. There are plenty of flowers, however, to which insects could seemingly be
of no use. They have stamens and pistils not only close together, but even in
contact, — shut up together in some cases, so that some of the pollen cannot fail
to be shed upon the stigma. Pea-blossoms, and those of most of the Pulse Fam-
ily are examples of this, having ten anthers closely surrounding one stigma, and
enclosed by a pair of the petals. And in the Showy Dicentra (or Bleeding-heart,
as it is popularly called, from the shape and color of the corolla), as in all the
‘rest of the Fumitory Family, six anthers are completely enclosed with one stigma,
three’ on one side and three on the other, in a cavity just large enough to hold
‘them: "This cavity is formed by the spoon-shaped summits of the two inner petals,
‘which never separate, being united only at their tips: those of the two outer
and ‘larger petals open and turn back. (See Figs. 9, 10.) One would say that
Such blossoms are purposely and effectually arranged to be fertilized without any
assistance, and to exclude all interference by insects. Yet they produce nectar

WHY PERFECT FLOWERS NEED TO ATTRACT INSECTS. 21

and are visited by bees. Is their nectar provided only for the good of the bee?
We might suppose so, until we come to know the remarkable fact that, unless
visited by insects, they seldom ripen a pod or set a seed. The Showy Dicentra,
which comes from Japan or Northern China, rarely sets fruit in our gardens in
any case. But the wild species of Corydalis and Fumitory, which have their
flowers on the same plan, seed freely enough. Yet when the blossoms are kept
covered with fine gauze, so as to exclude insects, little or no seed is produced.
Evidently then, for some reason or other, insects sucking their honey are not only
useful, but needful even to such blossoms. Why they should be needful remains
to be seen.

Fig. 9. Flower of Bleeding-heart, Dicentra spectabilis Fig. 10 Same, with the tips of the united inner petals pushed
to one side. Fig. 11. Tips of the six stamens and pistil, which are exposed in Fig. 10, here separated and dis-
played, magnified.

38. If it be wonderful that such flowers as the last do not well fertilize without
help, although constructed, as we should say, expressly to do it, equally wonderful
is it to find blossoms with anthers and stigma placed close together, but with some.
obstacle interposed, as shown on near examination ; which looks as if the object
were how not to do it.

39. Iris-flowers are of this sort. There is a stamen to each of the three stig-
mas, and close beside it. Behind each stamen and partly overhanging it is a
petal-like body, peculiar to Iris or Flower-de-Luce: these three bodies, appearing
like supernumerary petals, are divisions of the style, in a peculiar form, notched
at the end; under the notch is the stigma, in the form of a thin plate. We
notice that the stigma is higher than the anther ; but that is only a part of the

22 HOW PLANTS EMPLOY INSECTS TO WORK FOR THEM.

difficulty. The anther and the stigma face away from each other. The anther
faces outwards and discharges its pollen through two long slits on the outer side
only. The thin plate or shelf is stigma only on its upper or inner face, which is
roughened and moistened in the usual way for receiving the pollen: the face
turned towards the anther cannot receive the
pollen at all.

40. A less common flower, the beautiful
Arethusa, of our northern bogs (Figs. 13,
14), is quite as curiously arranged so as just
not to do of itself what is obviously intended
to be done. The stamen and the style are
united into a long and wing-margined col-
umn ; the stigma is a shelf; and the anther,
which is shaped like a helmet, and is fixed to
the top of the column by a hinge at the back,
rests upon this shelf, its front edge at bottom
projecting slightly over its edge, —just as
the lid of a chest projects a little over the
front side, for more convenient lifting. The

Fig. 12. Iris-flower cut len nthotee, aE anther holds four soft and loose pellets of

one stamen and stigma. pollen, which are ready to fall out when the
anther is uplifted. But here again, only the under side of the shelf is actually
stigma; the pollen lies imprisoned on the upper surface, and can never of itself
reach the lower surface, where alone it can act.

41. There are hundreds of such cases, differing more or less in the arrange-
ment, but agreeing in this, that the pollen is placed tantalizingly near the stigma,
yet where it can never reach it of itself, or can seldom and only accidentally do
so, Surely, if we had the making of these blossoms, we should have turned the
shelf under the anther of Arethusa the other side up, and have restored the har-
mony of that averted couple in Iris by turning the two face to face in place of
back to back.

42. The flower of Aristolochia Stpho, or Pipe-vine of the Southern States (a
large-leaved woody twiner which is cultivated for arbors), shows the same extra-
ordinary aversion in a different way. From its shape the blossom is called Dutch-
man’s-pipe : it is a tube curved round on itself, largest at the base, contracted at

WHY PERFECT FLOWERS NEED TO ATTRACT INSECTS. 23

the orifice, and then expanded into a flat border. At the very bottom of it is a
short and thick mass, consisting of a broad stigma, to the outside of which three
sets of anthers grow fast: these face away from the stigma, so that none of the
pollen can fall on it; and the crooked tube of the flower, with a narrow opening,.
must effectually prevent the wind from giving any aid. What can this mean?

43. To explain the puzzle which such flowers present, we have to consider that,
by their bright colors, or odors, or the nectar they offer, —- sometimes by all three
allurements combined, always by the latter, —they attract insects; by whose
usually rough or bristly heads, or legs, or bodies, pollen may be brushed out of
the anthers, or caught as it falls, and some of it carried to or dropped upon the
stigma. And we must infer that these blossoms are so constructed and arranged
on purpose that insects may visit and fertilize them; and that many species are
absolutely dependent upon such assistance: for, as they would not set seed, they
could not permanently exist, except for the insects which they nourish in return
for such service. So we conclude that honey is the wages paid to insects in
return for the work they do; and that the fragrance of flowers and their beautiful
colors, as well as their honeyed sweets, are not merely for our delight, and for the
use of the insects they feed, but are of primary use to the plant itself.

44, In confirmation of this view, it is found that flowers which are fertilized by
the wind, of which there are numerous sorts, produce neither bright-colored
corollas, nor fragrance, nor honey.

45. Now that we know the way of it, nothing is more interesting than to
notice how particular flowers, each in its own way, are arranged so as to be helped
by the insects that visit them. Iris-flowers (Fig. 12), for instance, are visited by
bees. These alight upon the outer and recurving, usually crested or bearded di-
visions of the flower, down the base of which is the only access to the nectar below.
When sucking out the nectar with its proboscis, the bee’s head 1s brought down
beneath the anther ; when raised, it will rub against it and brush out some of the
pollen: this, loosely adhering to its hairy surface, is ready to be deposited upon
the shelf of stigma above, not when the bee leaves the flower, but when it repeats
the action. When Arethusa (Figs. 13-15) is visited, the head of the bee enters
the mouth of the flower: in raising it to leave the flower after extracting the nec-
tar, the head hits the front edge of the helmet-shaped anther, raises it like a lid,
and receives one or more of the soft pellets of pollen that fall upon it: on again
entering the flower and again rising to depart, the pollen-loaded head is first

24 HOW PLANTS EMPLOY INSECTS TO WORK FOR THEM,

brought against the sticky stigma, which occupies all the lower face of the shelf,
and at the next instant raises the lid to receive another charge of pollen.

46. Before proceeding further to consider how particular flowers are arranged
to be helped by some particular sort or class of insects, and each in some pecu-
liar way, we should contemplate the remarkable conclusion to which we are
brought. It seems to be this: —- these flowers are so constructed that the pol-
len, however near the stigma, is somehow prevented from reaching it of itself, and
then honey and other allurements are provided to tempt insects to come and convey
the pollen to the stigma. And the various contrivances for hindering the pollen
from reaching the stigma directly are excelled only by those for having it done in
a roundabout way. So Nature appears to place obstacles in the way, and then to
overcome the difficulty of her own making by calling in the aid of insects! This
is blocking the wheels with one hand and lifting the vehicle over the obstruction
with the other. Or it is as if the wagoner of the fable, who prays Hercules to
help him out of the mire, had bogged his team merely for the sake of calling upon
Hercules. This is simply incredible. The explanation of one puzzle has brought
in its train a greater puzzle still.-

47. The solution of this puzzle is simple enough when once hit upon, although
it has taken a long time to find it out. It not only makes everything plain as
respects all these flowers, but also, as a true discovery should, clears up and
explains a great many things besides. The explanation is, that

48. Cross-Fertilization is aimed at. The pollen was not intended to fertilize that
same flower, but to be conveyed to some other flower of the same species. So in-
sects, which had seemed to be needful only when the stamens and pistils are in
separate flowers, or on separate plants, are quite as needful, — indeed, are more
needful — where these organs stand side by side in the same blossom. The rea-
son why crossing is advantageous, and in the long run necessary, is that

49. Breeding-in-and-in is injurious. Close-fertilization, that is, the fertilization of
the seeds by pollen from the same flower, is very close breeding indeed. It is
the next thing to no fertilization at all in plants, that is, to propagation by buds,
— which may go on, as we know, for a long time: but it is not probable that any
species could always continue in that way. Cultivators and stock-breeders are
obliged to close-breed to keep a particular race of few individuals true and to
heighten its desirable qualities. But sooner or later (in animals soon), more or
less wide breeding is necessary to keep up vigor and fertility. Wide-breeding is

AND CROSS-FERTILIZE TUEIR FLOWERS. 25

naturally secured by the structure itself in plants with separated flowers, — most
completely in those which, like Willows, bear stamens and pistils upon different
trees. And in the majority of plants which have perfect flowers it is commonly
no less secured by arrangements of various kinds for excluding the pollen from its
own stigmas, and having it conveyed to those of some other flower of the same
species.

50. Comprehending now the full meaning of these curious arrangements, we
may turn back to some of the flowers already noticed, to observe how exqui-
sitely they are adapted to the purpose in view, and then advance to new and more
varied illustrations.

51. Cross-Fertilization in Iris (Fig. 12). A little nectar is produced in the bot-
tom of the tube or narrow cup of the blossom. The only access to it is a narrow
channel leading down the united bases of the six divisions or leaves of the flower.
Now the three inner of these are upright, with their tips curved inwards, shutting
off all access in that quarter. But the three outer and larger divisions recurve
and afford a convenient landing-place directly before the stamen and the over-
arching stigma. Here the bee alights. To reach and suck out the nectar with
his proboscis will bring the head at least as low as the base of the anther. On
raising his head to depart he sweeps with it the whole length of the anther ana
dusts it with the pollen now shedding. A little higher the shelf of stigma is hit,
but only the outer face of it, which is smooth and does not take the pollen at all.
Flying to the next blossom, the first thing which the pollen-powdered head of the
bee strikes is the stigma, but this time on the upper face of the shelf or real sur-
face of stigma, which takes some of the pollen brought into contact with it, and
so is fertilized. Sinking lower, the head next brushes the anther downwards in
entering for the nectar, then upwards in departing, and receives a fresh charge of
pollen to be deposited upon the shelf of stigma of the next blossom visited, and
so on.

52. In Arethusa (40, 45, Figs. 13-15). We have never seen bees or other in-
sects about this flower; but it is plain from its structure that it cannot set seed
without their help. As already described, the bee, or other insect of considerable
size, can enter the blossom only in front; and the large and crested recurving
petal offers a convenient landing-place. At the bottom of the narrowed cup of
the flower a little nectar is produced, down to which the insect must reach its
proboscis. In rising to escape, its head must strike the lower face of the over-

26 HOW PLANTS EMPLOY INSECTS TO WORK FOR THEM,

hanging shelf, which is stigma, and so sticky that any pollen it may chance to
have brought would be left adhering there. As the head slips by, it must next
hit the front edge or visor of the hel-
met-shaped anther, raise it on its hinge,
and so allow one or more of the four.
loose pellets of pollen to drop out, or
be brushed out by the insect’s head, to
which some of the pollen would stick.
When the next flower is entered noth-
ing is accomplished ; but on departing,
as before, any pollen on its head would
be applied to the sticky shelf of stigma
overhead, the lid then uplifted, and a
fresh charge of pollen taken from this
flower to be given to the next, and
80 on in succession.

Fig. 13. Flower of Arethusa, entire. Fig. 14. A section 53. It is not unlikely

lengthwise. that the pellets of pol-

len, as they fall out of the uplifted anther of Arethusa, may some-
times miss the insect’s head, or fail to adhere to it, and so be lost.
But this plan, or something like it, serves the purpose in the por-
tion of the Orchis Family of which Arethusa is the representative.
In others of that family the result is made surer by considerably
different, more economical, and wonderfully curious arrangenients,
—such especially as those

54. In Orehises and other plants of that particular tribe of the Mg-,16._Disgram
Orchis Family. There is only one true Orchis in this country, and peje erie
that not common, except northward. And its arrangement for fer- Position.
tilization is not quite so readily understood as in those Orchises which are named
by botanists Habenaria, of which we have many species. Some of these are plen-
tiful, such as the Fringe Orchises, either the purple, white, or yellow species.
The Greater Green Orchis is not so common, but is taken for the present illustra-
tion on account of the size of its blossoms. A reduced figure of it, with its two
large round leaves spreading on the ground, and its spike of flowers rising be-
tween them on a naked stalk, is m the foreground of the vignette title, and a
single blossom, of only twice the size of life, is represented in Fig. 16.

t

AND CROSS-FERTILIZE THEIR FLOWERS.

55. The peculiarities are mainly these :
First, the better to attract certain insects
and repay them for their service, a sepa-
rate organ for the nectar—in this in-
stance a long pouch or honey-tube — is
attached to the flower. Then, to econo-
mize the pollen, the whole of it in each
cell of the anther is done up in little
packets or coarser grains, which are tied,
as it were, to each other by delicate
elastic threads, and all made fast by
similar threads to the upper end of a
central stalk. Finally, to make sure of
its being taken by the insect and not
dropped or lost in the carrying, the
other end of this stalk bears a flat disk,
commonly button-shaped, the exposed
face of which is very sticky ; and this is
placed just where it will be pretty sure
to be attached to the head or proboscis
of an insect that comes to drain the
honey-tube. So that the insect, on ris-
ing from his meal, will probably carry off
bodily the whole pollen of that flower
(or of one of its anther-cells), and be-
stow it, or some of it, upon the next
flower or flowers visited.

56. In this particular species, the front
petal is, as usual, the insect’s landing-
place. The other petals are more arch-
ing than the front view of the flower in
Fig. 16 represents, and obstruct access
on all other sides. The long and narrow
front petal turns downwards and allows
convenient approach. Underneath hangs

Fig. 16. Flower of Greater Green Orchis (Habenaria
orbiculata). 17. Its st: and stigma more enlarged.
18. One of the pollen-masses with its stalk and disk,
equally enlarged. 19. Its'disk anda part of the stalk
more magnified.

28 HOW PLANTS EMPLOY INSECTS TO WORK FOR THEM,

the honey-tube, its mouth opening just behind the base of this petal. Only the
lower half of the tube, more enlarged and capacious, gets filled with nectar. To
drain a cup which is about an inch and a half
deep requires a long proboscis, much longer
than any bee or wasp possesses. Butterflies
and moths are our only insects capable of do-
ing it; and one could predict from a view of
the flower that the work is done by them. In
fact we have hardly a butterfly with proboscis
long enough to reach the bottom of the cup:
so we conclude that one of the Sphynxes or
Night-moths, such as flock around the blos-
soms of the largest Evening-Primroses at dusk,
is the proper helpmate of the Greater Green
Orchis. The Smaller Green Orchis is much
like the Larger, but with honey-tube hardly an
Fig. 20. Side view of head of a moth (Sphynx inch long. This may be drained by many of
aeet a extracted @ our butterflies. Some of these have been
caught with a remarkable body attached to
their great eyes, one on each eye; on exam-
ination this body proved to be quite like that
represented in Fig. 18, only smaller. This
body, as we have seen, is the pollen of one
of the cells of an Orchis anther, with its
stalk and sticky disk, the latter adhering to
the insect’s eye. How did it get there?
57. The centre of the flower (as in Fig.
Tig.21 Front view of the same, with the pollen- 16) ig occupied by the one large anther, and
Masses in the position they soon take. Both
figures magnified to the same degree as is the by the concave stigma. The anther is of
Srebindomer tule: IS two cells, which taper towards the front of
the flower and diverge, in this species widely, and the whole space between the
two diverging horns on the sides and the orifice of the honey-tube below is stigma,
a broad patch of glutinous surface. At the tip of each horn of the anther, facing
forwards and partly inwards is the button-shaped, sticky disk. Bring the point
of a blunt pencil, or the tip of the little finger, or anything of the proper size,

AND CROSS-FERTILIZE THEIR FLOWERS. 29

down into the flower so as to press gently upon these disks for a moment; then
withdraw it: the disks will stick fast, and the stalks with the pollen-mass be
drawn out of the anther. Now the tip of the finger or the pencil is just in
the position which the head of the large butterfly or moth would occupy when
its proboscis is thrust deep into the honey-tube. In draining the nectar from
the tube the insect’s head is brought down close to its orifice, its large projecting
eye on one side or the other, or on both at once, is pressed against the sticky but-
ton ; and when the moth raises its head and departs, it carries away bodily one
or both of the pollen-masses. With these the next flowers visited may be ferti-
lized.

58. Except by the insect’s aid as a carrier, secured by this most elaborate and
wonderful contrivance, these Orchis flowers could never be fertilized. Close as
the pollen is to the stigma, it evidently cannot reach it by any ordinary chance.
And it would appear as if the obstacles were not effectually overcome even when
a moth or butterfly is so ingeniously employed to convey the pollen from one blos-
som to another, which is plainly what is intended. For the position of parts is
such that when the pollen-masses are extracted by the moth’s head, they will
stand pointing upwards and forwards, as shown in Fig. 20. The stalk is too stiff
to allow them to subside by their own weight. So when the moth alights upon _
the next flower and thrusts its proboscis down its honey-tube, the pollen-masses it
has brought would hit the anther, quite above the stigma, and effect nothing.
But all this is accurately provided for. As may be seen by watching the pollen-
masses when taken upon the point of a pencil, within from ten to thirty seconds
their stalk turns downward, as if upon a joint between it and the adhering disk,
bringing them into a position like that represented by a front view in Fig. 21.
Now the pollen-masses will accurately strike the stigma !

59. In some Orchises, and where this adjustment is needful, the pollen-masses
on the insect’s head not only turn downwards but converge inwards, always in the
way and to the degree necessary for their striking the stigma. In the larger
Green Orchises, from which the illustrations are drawn, the sticky disk is almost
parallel with the stalk of the pollen-mass at its lower end, and attached to it by a
short intermediate joint, as shown in Fig. 18, and more magnified in Fig. 19. It
is nearly the same in the Yellow and the White Fringed Orchises, which flower
later in the season. In all these the disks face partly inwards, at considerable
distance apart, and are stuck to the eye of the butterfly that visits them. In

30 HOW PLANTS EMPLOY INSECTS TO WORK FOR THEM,

others the disks are borne directly upon the end of the stalk, are generally closer
together, and get applied to the front of the head, or sometimes to the proboscis
of the insect.

60. When a pollen-mass, thus carried on the head of an insect, is brought mto
contact with the stigma, some of the pollen will cleave to its glutinous surface
and be left there, the little threads that bind it to the stalk giving way; another
portion will be left upon the stigma of the next flower visited, perhaps on the next
also, and so nearly all the pollen be turned to good account. Sometimes the ad-
hesion of the disk to the insect’s eye is less strong than the threads that bind the
grains to the stalk on the one hand, and than the adhesion to the stigma on the
other. Then the whole pollen-mass is left upon the stigma of that flower, and its
pollen taken in turn, to be exchanged for that of the next flower; and soon. In
any case each blossom will be fertilized by the pollen of some other blossom,
which is the end in view; and a more ingenious contrivance for the purpose can-
not be imagined.

61. The student should see all these curious things with his or her own eyes, in
order fully to comprehend and enjoy them. Once understood in our common wild
Orchises, it will be equally interesting to find out how it is done, in more or less
different and varied ways

62. In other Orchids, — whether wild ones, such as Ladies’ Tresses, Calopogon,
etc., or in those various and more gorgeous ones, mostly air-plants of tropical re-
gions, which adorn rich conservatories. Some of these curiously resemble butter-
flies themselves, — either a swarm of them, as some of the smaller ones in a clus-
ter on a long light stalk, fluttering with every breath of air ; some are like a large,
single, gorgeous, orange and spotted butterfly: Oncidium Papilio, for example
(Fig. 22), which takes its name from the singular likeness, Papilio being Latin for
butterfly ; and Phalenopsis, a plant of which, greatly reduced in size, is represented
on the vignette title-page (upper right-hand corner), with large white flowers,
takes its name from its resemblance to a moth. Can the likeness be a sort of
decoy to allure the very kinds of insect that are wanted for fertilizing these same
flowers? Sometimes the strange shapes are not like insects; the flowers of
Stanhopea tigrina, for example (figured at the top of the vignette title-page),
resembling in color and form rather the head of a cuttle-fish than any known
insect.

63. In Lady's-Slipper, or Cypripedium, the plan for securing fertilization is so dif-

AND CROSS-FERTILIZE THEIR FLOWERS. 31

ferent from that of any other of the Orchis Family as to need a separate descrip-
tion, but a very brief one must serve, as we have no figure ready. We refer to our
wild species ; and first to the
yellow ones and to the large
white and pink one, Cypri-
pedium spectabile, the Showy
Lady’s-Slipper. Unlike other
Orchids, there are two sta-
mens: the pollen is powdery, or
between powdery and pulpy,
and not very different from
that of ordinary flowers. As
it lies on the open anther in a
broad patch, it soméhow gets
a film like a thin coat of sticky
varnish. The stigma is large,
flat, and somewhat trowel-
shaped, the face turned for-
wards and downwards: it is
supported on a stout style, to
which the anthers have grown
fast, one on each side. This
apparatus is placed just within Fig. 22. Oncidium Papilio. Fig. 23. Comparettia rosea. Both
the upper part of the sac or are Epiphytes, or Air-plants, and reduced in size.

slipper (rather like a moccason or buskin than a slipper), which gives name to the
flower. There are three openings into the slipper; a large round one in front,
and the edges of this are turned in, after the fashion of one sort of mouse-trap ;
two small ones far back, one on either side, directly under each anther. Flies and
the like enter by the large front opening, and find a little nectar apparently be-
dewing the long hairs that grow from the bottom of the slipper, especially well
back under the overhanging stigma. The mouse-trap arrangement renders it dif-
ficult for the fly to get out by the way it came in. As it pushes on under the
stigma it sees light on either side beyond, and in escaping by. one or the other of
these small openings it cannot fail to get a dab of pollen upon its head, as it
brushes against the film with which the surface is varnished. Flying to the next

32 HOW PLANTS EMPLOY INSECTS TO WORK FOR THEM,

blossom and entering as before, as the insect makes its way onward, it can hardly
fail to rub the pollen-covered top of its head against the large stigma which forms
the roof of the passage. The stigma of every other Orchid is smooth and glu-
tinous. This is merely moist and finely roughened: the roughness comes from
very minute projections, all pointing forwards, so that the surface may be likened
to that of a wool-card or of a rasp on a very fine scale. So, as the insect passes
under, the film of pollen is carded or rasped off its head by the stigma and left
upon it; and when the fly passes out it takes a fresh load of pollen on its head
with which to fertilize the next flower. This mode of action we first predicted
fromm an inspection of the flower and a simple experiment. It has since been con-
firmed by repeated observations. The early-flowering and purple Stemless Lady’s-
Slipper differs from the others in having its larger slipper or sac pendent, and
with a long slit in front, instead of a round open orifice ; the two lips of the slit
are mostly in contact, but the fly may readily push its way in; the way of exit
is more open than in the other species.

64. In Asclepias or Milkweed. Now and then the rough legs of butterflies and
bees are found to be encumbered with bodies sticking to them which resemble the
pollen-masses of Orchids; but there is always a pair of them, of waxy
appearance, hanging by a curved stalk from a dark-colored disk, if it
may be so called, which is not button-shaped. These are the pollen-
masses of Milkweed, carried off by insects alighting on the flower to
suck the nectar from five little cups, and, sticking fast to their legs or

feet, are so carried from flower to flower. Fig. 24 shows a pair of

Ta ee them. Milkweeds are like Orchids in this respect only. Their flow-

of Milkweed. erg are very different and peculiar, not readily to be explained ex-

cept with the plant itself in hand; but insects are equally necessary to fertilize
them.

65. How ordinary blossoms are cross-fertilized by insects passing continually
from flower to flower will be obvious enough after these explanations, But ob-
serving eyes will detect many curious arrangements in the commonest plants, now
that the way is pointed out. A few may be described.

66. In Barberry-blossoms there is a remarkable peculiarity. We have learned, in
the first chapter, that certain plants are endowed with the power of moving some
part freely in order that they may climb. Barberry-blossoms have a movement
upon irritation, which has long been familiar as a mere curiosity, but which we

AND CROSS-FERTILIZE THEIR FLOWERS. 33

now begin to understand the meaning of. It is turned to account in fertiliza-
tion. The six stamens surround a pistil, but diverge away from it, as if to be
sheltered, one under each of the concave or arching petals. There
they remain unless touched, as with a pin or any other body, at the
base of the filament on the inside; then the stamen starts forward |
suddenly, as with a jerk, into an erect position. Not far enough for-
ward, however, for the anthers to hit the stigma ; indeed, the filament
is not quite long enough for that. Now the anther opens in an un-
usual way, namely, by trap-doors, one on each side (as shown in Fig. j
25), letting the pollen drop out. Barberry-blossoms are visited by ¥ig-25. Stamen
honey-bees and by smaller flying insects ; in the common Barberry the ere a
flowers are hanging. A touch by the proboscis of a bee hovering un- oe trap-
derneath causes the stamens in turn to spring forward suddenly, and to

shower the insect plentifully with their pollen. Some of this may be applied im-
mediately to the button-shaped stigma of that very flower; but some would
surely be carried to the stigma of the next flowers visited, and so on. In species
with upright flowers, the pollen will dust the proboscis and head of the bee, or
of smaller inséct crawling to the bottom for the nectar there; and in entering a
subsequent blossom it must needs brush this pollen against its stigma.

67. In Kalmia (American Laurel, and equally in the smaller species, namely,
Sheep Laurel or Lambkill, and in the earlier-flowering Glaucous Laurel of the
bogs), a mechanical instead of a vital movement is turned to similar account.
The singular structure of the blossom has long been known; the operation of it
is only now understood.

68. This is the plan of it. Ten stamens with slender filaments surround a
still longer style : the tip of the style is the stigma, which the pollen is somehow
to reach. But the anthers in the flower-bud lie in as many pouches in the sides
of the corolla (Fig. 26). When the corolla opens and takes its saucer-shaped
form, the anthers remain lodged in the pouches, so the filaments are: bowed back
and become so many springs (Figs. 27, 28). If untouched the springs generally
remain set until the corolla begins to fade: by that time the filaments lose their
elasticity and become flabby also. If we jostle them, however, by a somewhat
rude touch when the flower is in fresh condition, so as to liberate the anther, the
filaments straighten elastically and suddenly, and generally curve over in
the opposite direction. As they fly back they discharge a quantity of pollen.

3

34 HOW PLANTS EMPLOY INSECTS TO WORK FOR THEM,

Take notice that these anthers do not open by trap-doors, like those of Barberry,
nor by long slits as in most flowers. As in most of the Heath Family (to which
Kalmia belongs), they consist of a pair of sacs, side by side, which open by a
round hole at the top (see Fig. 29). So, when the bowed filament is set free and
‘flies forward, the grains of pollen in the anther are projected, like shot from a
child’s pea-shooter. A bit of whalebone, to the end of which two pieces of quill
filled with small shot are made fast, is not a bad representation of one of these
stamens. This really must be a contrivance for discharging pollen at some object.
If the stigma around which the stamens are marshalled be that object, the target
is a small one, yet some one or more of the ten shots might hit the mark. But
the discharges can hardly ever take place at all without the aid of an insect.
Bees are the insects thus far observed to frequent these flowers ; and it is inter-
esting to watch the operations of a bumble-bee upon them. The bee, remaining
on the wing, circles for a moment over each flower, thrusting his proboscis all
round the ovary at the bottom; in doing this it jostles and lets off the springs,
and receives upon the under side of its body and its legs successive charges of
pollen. Flying to another blossom, it brings its pollen-dusted body against the
stigma, and, commonly revolving on it as if on a pivot while it sucks the nectar
in the bottom of the flower-cup, liberates the ten bowed stamens, and receives
fresh charges of pollen from that flower while fertilizing it with the pollen of the
preceding one. This account is founded on the observations of Professor Beal, of
Michigan, who also states that when a cluster of blossoms is covered with fine
gauze, no stamen gets liberated of itself while fit for action, and no seed seta.

Figs. 26-29. Flower of American Laurel, Kalmia latifolia. 26. Flower-bud divided lengthwise. 27.
Open flower. 28. Section of same, lengthwise. 29. A stamen enlarged, discharging pollen from
the two holes at the top.

AND CROSS-FERTILIZE THEIR FLOWERS, 35

69. One might doubt whether such movements as those of the stamens of Bar-
berry and of Kalmia were really intended for the use here assigned to them.
But they serve this purpose, unquestionably, and we can think of no other. Now
there is a flower of a tropical Orchid, cultivated in some conservatories (named
Catasetum), in which a movement under irritation (analogous to that of the Bar-
berry-stamen) and one of elasticity (like that of Kalmia) are combined in one
apparatus, — one so elaborate and special that nobody can doubt that it is a con-
trivance for this particular purpose. It cannot well be described here without
numerous figures and much detail. But the amount of it is, that a sensitiveness
of two slender and partly crossed arms, which the moth or other large insect’ must
hit in reaching the flower-cup, liberates a pollen-mass which is set as a spring, and
lets it fly like a catapult ; it hits the head of the insect at some distance, disk-end
foremost, and sticks fast to it, in proper position to be applied to the stigma of the
next proper flower visited.

70. Returning to flowers of ordinary structure, and of familiar kinds, two par-
ticular arrangements for insuring cross-fertilization in perfect flowers must be
briefly noticed. The commonest is that of

71. Dichogamous Flowers. Dechugamy is the name given to the case in which
the stamens and the stigmas of the same blossom come to perfection at different
periods. That is, the anthers mature and discharge their pollen in some platits
before the stigma is ready to receive it, in others only after the stigma has with-
ered. Either way, the pollen that fertilizes and the stigma that is fertilized can
never belong to the same blossom.

72. In the Common Plantain of our dooryards and waysides, Plantago major, and
in the English Plantain, or Ripple Grass (P. danceolata) of the fields, this is famil-
iarly illustrated. The style projects from the apex of the closed bud, ready to
receive pollen from other flowers a day or two before its stamens are hung out
upon their slender filaments, to furnish pollen for other flowers, —not for their
own, the stigma of which is by that time dried up. Plantain-flowers, however,
produce no nectar, and are neither fragrant nor brightly colored; so they aré not
visited by insects, but are left to the chance of the conveyance of the pollen by
the wind. It is the same with many Grasses and Grains, only in reverse order.
Their anthers hang out on their slender filaments one morning, and the feathety
stigmas of that blossom not until the next morning; and the wind is the pollen-
carrier.

36 HOW PLANTS EMPLOY INSECTS TO WORK FOR THEM,

73: In Figwort or Serophularia, and in many other flowers of which this may
serve as an example, the work is done with much saving of pollen by calling in
the aid of insects. Fig. 30
is an enlarged representa-
tion of one of the flowers,
as it appears throughout
the day of opening. The
style projects from the
gorge of the corolla, pre-
senting the stigma just
over the front edge. The
stamens are out of sight

Fig. 30. Flower of Scrophularia nodosa, the first day. 31. Inside view of and reach, and not yet
it, the front half cut away. 82. Flower as it appears on thesecond day. ready: they lie recurved
below, as shown in Fig.
31. A day or two later the fiower appears as in Fig. 32: the style is flabby or
withering, and the stigma aried up; the stamens have straightened their fila-
merits, and have brought up the four now opened anthers above the front edge of
the corolla, where the stigma was the day before. The bottom of the corolla-
cup contains some nectar. Honey-bees are attracted by it. When they visit a
flower in the state of Fig. 32, alighting as they do on the front lip, they get the
chest and legs well dusted with pollen, none of which has acted upon its own
stigma ; for that was dry and effete before these anthers opened. When the bee
passes to a freshly expanded flower, such as Fig. 30, the parts covered with pol-
len are sure to be brought against the fresh and active stigma, which cannot have
possibly. been touched by any pollen of that flower, its anthers being still imma-
ture and hidden below.

74. In some other Flowers the pollen is conveyed from an earlier to the stigma
of a later blossom, the anthers maturing and shedding their pollen before the
stigma is ready to receive any. A beautiful case of the sort, in which a move-
ment comes conspicuously into play, may be seen in Clerodendron Thompsonie, a
climbing shrub from tropical Africa which blooms in our conservatories. Four
stamens with very long filaments and an equally long and slender style are rolled
up together in the corolla-bud. When this expands, the stamens straighten out
nearly in the line of the tube of the corolla, and their anthers open: the style

AND CROSS-FERTILIZE THEIR FLOWERS. 37

has bent so far forwards as to point downwards, and the stigma is not yet ready for
pollen, its two branches being united. So a butterfly, in the act of drawing nectar
from this flower, will get the under side of its body dusted with pollen, but will
not come near the reflexed and still immature style. But in a flower a day older,
the stamens are found to be coiled up (the opposite way from what they were in
the bud) and turned down out of the way, bringing the anthers nearly where the
stigma was the day before; while the style has come up to where the stamens
were the day before, and its stigma with branches outspread is now ready for
pollen, — is just in position and condition for being dusted with the pollen which
the butterfly has received from the anthers of an earlier blossom.

75. Campanulas and Sabbatias also mature their anthers and shed their pollen
long before the stigmas open so as to receive any; they, too, are fertilized by in-
sects carrying pollen from an earlier to a later flower. To understand how it is
done in each particular case the flowers themselves should be studied in the field
and garden.

76. Dimorphous Flowers, that is, flowers of two kinds as to length or position of
stamens and pistil, but both sorts perfect, remain to be considered. In these the
difference is only in the stamens and pistil, usually merely in their relative length,
and very likely to be noticed only by the attentive observer. A good case of this
may readily be seen

77. In Houstonia, The com-
monest species, the little blue-
eyed Houstonia coerulea, looks
up to us from every low mead-
ow in spring as soon as the turf
gets dry enough to set foot
upon. In different patches of
it, some flowers will show the
tips of the four stamens slight-
ly projecting ; as many others
will show the two stigmas
only. The two kinds are al-

‘ iff hes: all Figs. 83, 35. The two sorts of flower of Houstonia exrulea. 84
ways 1n different pate €8; and 36. Same more enlarged, with corolla divided and laid

that come from the same seed open.
being alike. The sort that shows the tips of the anthers (as in Fig. 33, and with

38 HOW PLANTS EMPLOY INSECTS TO WORK FOR THEM,

corolla divided and spread open in Fig. 34) has a short style, which brings the
two stigmas up to near the middle of the tube of the corolla. The sort that
shows the stigmas projecting (as in Figs. 35 and 36) has the style long enough to
bring them up just to the place which the anthers occupy in the other flower;
but its anthers are placed as low down in the tube as the stigmas are in the first
flower. The little Partridge Berry of the woods has its flowers of two sorts, on
the same plan: and among garden flowers it may be seen in Primroses. But it
is to be noted that this plan occurs only in flowers that are frequented by insects.

78. In the Houstonia, small insects, feeding by a proboscis, passing from flower
to flower, take from the high-stamened one (Figs. 33, 34) some pollen upon the
face, as it is brought down close to the orifice of the corolla when the proboscis
is thrust to the bottom for the nectar there. When the insect passes to another
flower of the same sort, it merely gets its face smeared with a little more pollen.
But when it visits a long-styled flower (such as Figs. 35, 36) and brings its head
down to the orifice, it will apply some of this pollen to the stigmas, which are
exactly in the position to receive it. So the high anthers are to fertilize the high
stigmas. How about the low stamens and low stigmas, when the insect flies from
a. flower of the second sort to one of the first, as it is quite as likely to do?
Why, the insect’s proboscis, as it explores that flower, gets dusted with the pollen
of the low anthers, and this pollen is neatly carried and applied to the similarly
placed stigma of the other kind of flower. So much for dimorphous flowers.
There are even

79. Trimorphous Flowers, that is, perfect flowers of three sorts arranged to co-
operate in this way. One case at least was discovered by the most sagacious
investigator of this whole class of subjects (Mr. Darwin), in a kind of Loosestrife
(Lythrum Salicaria), and there is something nearly like it in another bog plant of
the Loosestrife Family, Weswa verticillata. There are three lengths of style and
three lengths of stamens, two of the latter in each sort of flower, the stamens
being in two sets. Bees suck the flowers of this Loosestrife. In doing so, the
longest stamens rub their pollen against the lower and hinder part of the body
and the hind legs; the middle-length stamens, between the front pair of legs;
the shortest stamens, against the proboscis and chin. When they fly to other
flowers, the very parts that are dusted with long-stamen pollen rub against the
stigma of the long style; those dusted with that of middle-length stamens,
against the stigma of middle-length style ; those with that of short stamens, against

AND CROSS-FERTILIZE THEIR FLOWERS. 39

the stigma of the shortest style, — each to each. Not only is the pollen, through
such wonderful arrangements, so distributed as to secure cross-fertilization, but
the end is further secured by a

80. Preference of Stigma for Pollen of other Flowers than its own, In dimorphous
and trimorphous flowers, such as have just been described, it has been ascertained
that if pollen is placed upon the stigma of the same blossom, or even on that of
another blossom of the same sort, it takes little or no effect. There are cases
where the stigma gets naturally covered with its own-flower pollen without set-
ting seed, but when touched with the pollen of another flower it seeds perfectly.
This explains, at length, the remarkable thing (described in paragraph 37) that
the blossoms of Peas, Beans, and of Dicentra or Bleeding-heart and the like,
generally set little or no seed when insects are excluded, although the parts are
so disposed that the stigma must be dusted by the pollen of the stamens enclosed
with it. Why even such flowers need the aid of insects is now clear. This pref-
erence of pollen for other than its own blossom, however, is strictly

81. Within the limits of the Species. The pollen which is conveyed to the stigma
of a different species is inactive and without result, in all but species that are
pretty nearly related, and in many of these. Apple-blossom pollen, for instance,
does not fertilize pear-blossoms, and vice versa. Cross-breeding among flowers
of the same species is the rule, — among different species the exception. It may
be done, however, to a certain extent, but always with more difficulty ; it rarely
occurs in nature left to itself. Crossing of species produces Hybrids : by recourse
to it gardeners and florists greatly diversify certain flowers and fruits ; for the new
sorts produced inherit from both parents: the cultivator aims at originating and
preserving those that combine the most desirable qualities of both parents.

82. Advantage of Perfect Flowers. The greater number of species, and far the
greater number of those that are visited by insects, are perfect, that is, with sta-
mens and pistil in the same blossom. Yet separated flowers would seem best for
the end in view, cross-fertilization in them taking place of necessity. But, with
insects to assist, it is better, that is, more economical, to have perfect flowers ;
for, while the crossing is equally secured, buth flowers produce seed. ‘‘ The econ-
omy of Nature” of which we read is something more than a figure of speech.

83. The reciprocity of flower and flower, and of insects and flowers, is some-
thing admirable. Insects pay liberal wages for the food which flowers provide for
them. The familiar rhymes of Dr. Watts directed the attention of young people

40 HOW PLANTS EMPLOY INSECTS TO WORK FOR THEM.

to the bee visiting the flower as a model of industry. With a slight change of a
couplet, adapting it to our present knowledge and to the lesson of mutual help-
fulness, we may read : —
How doth the little busy bee
Improve each shining hour,
While gathering honey day by day,
To fertilize each flower.

84. Such are the principal modes, thus far known (and when these are under-
stood watchful eyes may discover other equally curious cases), in which flowers
are prevented from breeding in and in, either wholly or to such extent as
to keep up the vigor of the species. Such are some of the ways in which
flowers are adapted to insects, and no doubt insects to flowers, for this end.
Plants, destitute of the locomotion and volition which animals, at least the higher
animals, enjoy, have the lack made up to theni in these subtle and very various
contrivances, by which the volition and locomotion of insects are made to serve
them, even to secure their very existence. For, to say that these plants could
continue to flourish without such aid is tantamount to saying that these multi-
farious, elaborate, and exquisite arrangements are superfluous, — which is past all
belief.

85. It is equally past belief that they are undesigned or accidental. No one
has been able to describe them except in language which assumes that they are
contrivances, adaptations for particular purposes, and the like ; and where many of
them are best described they are said to ‘transcend in an incomparable degree the
-contrivances and adaptations which the most fertile imagination of the most imag-
inative man could suggest, with unlimited time at his disposal.” Now, no matter
‘whether or not the flowers themselves with all these structures have been
‘perfected step by step, through no matter how long a series of natural stages,
— if these structures and their operations, which so strike the mind of the philos-
opher no less than of the common observer that he cannot avoid calling them
contrivances, do not argue intention, what stronger evidence of intention in Na-
ture can there anywhere possibly be? If they do, such evidences are countless,
and almost every blossom brings distinct testimony to the existence and provi-
dence of a Designer and Ordainer, without whom, we may well believe, not merely
@ sparrow, not even a grain of pollen, may fall.

HOW CERTAIN PLANTS CAPTURE INSECTS. 4]

CHAPTER III.

HOW CERTAIN PLANTS CAPTURE INSECTS.

86. Tuts is not a common habit of plants. Insects are fed and allowed to depart
unharmed. When captures are made they must sometimes be purely accidental
and meaningless ; as in those species of Szlene called Catch-fly, because small flies
and other weak insects, sticking fast to a clammy exudation of the calyxes in
some species, of a part of the stem in others, are unable to extricate themselves
and so perish. But in certain cases insects are caught in ways so remarkable that
we cannot avoid regarding them as contrivances, as genuine flytraps.

87. Flower-Flytraps are certainly to be found in some plants of the Orchis
Family. One instance is that of Cypripedium or Lady’s-Slipper, which, being a
contrivance for cross-fertilization, is described in the foregoing chapter (paragraph
62). Here the insect is entrapped for the purpose of securing its services ;
and the detention is only temporary. If it did not
escape from one flower to enter into another, the
whole purpose of the contrivance would be defeated.
Not so, however, in

88. Leaf-Flytraps. These all take the insects life,
—whether with intent or not it may be difficult
to make out. The commonest and the most ambig-
uous leaf-flytraps are

89. Such as Pitchers, of which those of our Sarra-
centa or Sidesaddle-flower are most familiar. Fig. 37
represents one leaf, and a section of another, of the
species most common in our bogs, especially at the
North ; and the vignette title-page, at bottom on
the right hand, shows the longer and more tubular
pitchers of another species of the Southern States.
S. flava, a common yellow-flowered species from

capers Fig. 87. Leaf of th Sa
Virginia southward, has them so very long and ‘cenia purpurea, and one cut across.

42 HOW CERTAIN PLANTS CAPTURE INSECTS.

narrow, that they are popularly named Trumpets. In these pitchers or tubes
water is generally found, sometimes caught from rain, but in other cases evi-
dently furnished by the plant, the pitcher being so constructed that water can-
not rain in: this water abounds with drowned insects, commonly in all stages of
decay. One would suppose that insects which have crawled into the pitcher
might as readily crawl out; but they do not, and closer examination shows that
escaping is not as easy as entering. In most pitchers of this sort there are sharp
and stiff hairs within, all pointing downward, which offer considerable obstruction
to returning, but none to entering.

90. Why plants which are rooted in wet bogs or in moist ground need to catch
water in pitchers, or to secrete it there, is a mystery, unless it is wanted to drown
flies in. And what they gain from a solution of dead flies is equally hard to
guess, unless this acts as a liquid manure.

91. Into such pitchers as the common one represented in Fig. 37 rain may
fall; but not readily into such as those of the vignette title already referred to, —
not at all into those of the Parrot-headed species, S. pstt-
tacina of the Southern States, for the inflated lid or cover
arches over the mouth of the pitcher completely. This
is even more strikingly so in Darlingtonia, the curious
Californian Pitcher-plant lately made known and culti-
vated : in this the contracted entrance to the pitcher is
concealed under the hood and looks downward instead of
upward ; and even the small chance of any rain entering
by aid of the wind is, as it were, guarded against by a
curious appendage, resembling the forked tail of some
fish, which hangs over the front. Any water found in
this pitcher must come from the plant itself. So it also
must in the combined

92. Pitcher and Tendril of Nepenthes. These Pitcher-
r plants are woody climbers, natives of the Indian Archi-

Fig. 38. Leaf-tendril and pelago, and not rarely cultivated in hot-houses, as a curi-

eee osity. One is shown on the vignette title, right-hand
side, and their way of climbing is mentioned in the foregoing chapter (19). Some
leaves lengthen the tip into the tendril only; some of the lower bear a pitcher
only ; but the best developed leaves have both, —the tendril for climbing, the

HOW CERTAIN PLANTS CAPTURE INSECTS. 43

pitcher one can hardly say for what purpose. The pitcher is tightly closed by a
neatly fitting lid when young; and in strong and healthy plants there is com-
monly a little water in it, which could not possibly have been introduced from
without. After they are fully grown the lid opens by a hinge; then a little water
might be supposed to rain in. In the humid sultry climates they inhabit it prob-
ably does so freely, and the leaves are found partly filled with dead flies, as in
our wild Pitcher-plants.

93. The drowning of insects in plant-pitchers is of course an accidental occur-
rence, and any supposed advantage of this to the plant may be altogether fanci-
ful. But we cannot deny that the supply of liquid manure may be useful. Be-
fore concluding that they are of no account, it may be well to contemplate other
sorts of leaf-flytraps.

94. Sundew as a Fly-catcher. All species of Sundew (Drosera) have their leaves,
and some their stalks also, beset with bristles tipped with a gland from which
oozes a drop of clear but very glutinous liquid, making the plant appear as if
studded with dew-drops. These remain, glistening in the sun, long after dew-
drops would have been dissipated. Small flies, gnats, and such-like insects, seem-
ingly enticed by the glittering drops, stick fast upon them and perish by starva-
tion, one would suppose without any benefit whatever to the plant. But in the
broad-leaved wild species of our bogs, such as the common Round-leaved Sundew
(figured, much reduced in size, at the foot of the vignette title, toward the right),
the upper face and edges of the blade of the leaf bear stronger bristles, tipped
with a larger glutinous drop, and the whole forms what we must allow to be a
veritable fly-trap.

95. For, when a small fly alights on the upper face, and is held by some of
the glutinous drops long enough for the leaf to act, the surrounding bristles
slowly bend inwards so as to bring their glutinous tips also against the body of
the insect, adding, one by one, to the bonds, and rendering captivity and death cer-
tain. This movement of the bristles must be of the same nature as that by
which tendrils and some leafstalks bend or coil. It is much too slow to be visible
except in the result, which takes a day or two to be completed. Here, then, isa
contrivance for catching flies, a most elaborate one, in action slow but sure. And
the different species of Sundew offer all gradations between those with merely scat-
tered and motionless dewy-tipped bristles, to which flies may chance to stick, and
this more complex arrangement, which we cannot avoid regarding as intended for

44 HOW CERTAIN PLANTS CAPTURE INSECTS.

fly-catching. Moreover, in one of our species with longer leaves (D. longifolia)
the blade of the leaf itself incurves (as an intelligent lady has observed), so as to
fold round ‘its victim ! larusin - of “/Psectiversds Plants

96. Another and a most practised observer, whose observations are not yet pub-
lished, declares that the leaves of the common Round-leaved Sundew act differ-
ently when different objects are placed upon them. For instance, if a particle of
raw meat be substituted for the living fly, the bristles will close upon it in the
same manner ; but to a particle of chalk or wood they remain nearly indifferent.
If any doubt should still remain whether the fly-catching in Sundews is acciden-
tal or intentional, in other words, whether the leaf is so constructed and ar-
ranged in order that it may capture flies, — the doubt may perhaps disappear
upon the contemplation of another and even more extraordinary plant of the
same family with the Sundew, namely,

97. Venus’s Flytrap, or Dionea muscipula. This plant abounds in the low savan-
nas around Wilmington, North Carolina, and is native nowhere else, It is not
very difficult to cultivate, at least for a time, and it is kept in many choice con-
servatories as a vegetable wonder.

98. The trap is the end of the leaf (see Figs. 39,
40). It is somewhat like the leaf of Sundew, only
larger, about an inch in diameter, with bristles still
stouter, but only round the margin, like a fringe, and
no clammy liquid or gland at their tips. The leaf
folds on itself as if hinged at the midrib. Three
more delicate bristles are seen on the face upon close
inspection. When these are touched by the finger or
the point of a pencil, the open trap shuts with a
quick motion, and after a considerable interval it
reopens. When a fly or other insect alights on the
surface and brushes against these sensitive bristles,
the trap closes promptly, generally imprisoning the
intruder. It closes at first with the sides convex and
the bristles crossing each other like the fingers of in-

i

Fig. 39. Leaves of Dionea or Ve- : :
rae Flytrap, the trap of the terlocked hands or the teeth of a steel-trap, as in the

larger one wide open. side figures of Fig. 39. But soon the sides of the
trap flatten down and press firmly upon the victim; and it now requires a very

HOW CERTAIN PLANTS CAPTURE INSECTS. 45

considerable force to open the trap. If nothing is caught the trap presently
reopens of itself and is ready for another attempt. When a fly or any similar
insect is captured it is retained until it perishes, —is killed, indeed, and con-
sumed ; after which it opens for another capture. But after the first or second it
acts sluggishly and feebly, it ages and hardens, at length loses its sensibility, and
slowly decays.

99. It cannot be supposed that plants, like boys, catch flies for pastime or in
objectless wantonness. Living beings though they are, yet they are not of a suf-
ficiently high order for that. It is equally incredible that such an exquisite
apparatus as this should be purposeless. And in the present case the evidence of
the purpose and of the meaning of the strange action is wellnigh complete.
The face of this living trap is thickly sprinkled with glands immersed in its tex-
ture, of elaborate structure under the microscope, but large enough to be clearly
discerned with a hand lens; these glands, soon after an insect is closed upon, give
out a saliva-like liquid, which moistens the insect, and in a short time (within a
week or two) dissolves all its soft parts, — digests them, we must believe ; and the
liquid, with the animal matter it has dissolved, is re-absorbed into the leaf! We
are forced to conclude that, in addition to the ordinary faculties and function of
a vegetable, this plant is really carnivorous.*

100. That, while all plants are food for animals, some few should, in turn and
to some extent, feed upon them, will appear more credible when it is considered
that whole tribes of plants of the lowest grade (Mould-Fungi and the like) habit-
ually feed upon living plants and living animals, or upon their juices when dead.
An account of them would make a volume of itself, and an interesting one. But
all goes to show that the instances of extraordinary behavior which have been

* Ellis, who first described the Dionea in full, and gave it this name noticed the liquid secretion and
the glands that produce it, but thought that it was given out while the trap was open and as a lure to
insects: he expressed his belief that the leaves caught insects for the purpose of nutrition. Linnseus
appears to have doubted this; he omitted all account of the fluid, and gave a more humane, but incor-
rect, version of the plant’s behavior, stating that the trap holds the insect only while it struggles, but
releases it on becoming quiet: and this statement has been commonly adopted. Elliott merely copied
the description by Linnzus. The Rev. Dr. M. A. Curtis of North Carolina (just deceased) gave a
more correct account about thirty years ago. Recently Mr. William M. Canby of Delaware has pub-
lished some very interesting observations and experiments; which show that the liquid is a sort of gas-
tric juice, exuded after the capture. He also fed the leaves with morsels of raw beef, and found that
these in most instances were mainly dissolved in the juice, which then disappeared, evidently by ab-
sorption. Similar observations and experiments made by Mr. Darwin are still unpublished.

ef P: ¢

46 HOW CERTAIN PLANTS CAPTURE INSECTS.

recounted in these chapters are not mere prodigies, wholly out of the general
order of Nature, but belong to the order of Nature, and indeed are hardly dif-
ferent in kind from, or really more wonderful than, the doings of many of the
commonest plants, which, until our special attention is called to them, ordinarily
pass unregarded.

Fig. 40. Venus’s Flytrap: Dionsa.