94

SEEDS WHICH MIMIC ANIMALS.

[CHAP.

the resemblance is even more striking. The seeds have a central line resembling the space between the

FIG. 57:

elytra, dividing and slightly diverging at the end, while between them the end of the abdomen seems

IV.]

BISERRULA, RICINUS, JATROPHA.

95

to peep; at the anterior end the seeds possess a small lobe, or caruncle, which mimics the head or thorax of the insect, and which even seems specially arranged for this purpose; at least it would seem from experiments made at Kew that the carunculus exercises no appreciable cffect during germination. In Trichosanthes anguina the long pods hang down, and alike in size, form, colour and attitude closely resemble snakes, as the specific name denotes.

These resemblances might benefit the plant in one of two ways. If it be an advantage to the plant

FIG. 58.-Pod of
Biserrula.

FIG. 58a.-Seed of
Castor Oil (Ricinus).

FIG. 586.-Seed of
Tatropha.

that the seeds should be swallowed by birds, their resemblance to insects might lead to this result. On the other hand if it be desirable to escape from graminivorous birds, then the resemblance to insects would serve as a protection. We do not, however, yet know enough about the habits of these plants to solve this question.

Indeed, as we have gone on, many other questions will, I doubt not, have occurred to you, which we are not yet in a position to answer. Seeds, for instance, differ almost infinitely in the sculpturing of their

96

PROBLEMS STILL UNSETTLED. [CHAP. IV.

surface. But I shall wofully have failed in my object if I have given the impression that we know all about seeds. On the contrary, there is not a fruit or a seed, even of one of our commonest plants, which would not amply justify and richly reward the most careful study.

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

FIG. 59.-The Beech.

CHAPTER V.

LEAVE S.

MR. RUSKIN, in one of his most exquisite passages, has told us that "Flowers seem intended for the solace of ordinary humanity: children love them; tender, contented, ordinary people love them. They are the cottager's treasure; and in the crowded town mark, as with a little broken fragment of rainbow, the windows of the workers in whose heart rests the covenant of peace." I should be ungrateful indeed

H

98

VARIETY OF FORMS.

[CHAP.

did I not fully feel the force of this truth; but it will be admitted that the beauty of our woods and fields is due at least as much to foliage as to flowers.

In the words of the same author, "The leaves of the herbage at our feet take all kinds of strange shapes, as if to invite us to examine them. Starshaped, heart-shaped, spear-shaped, arrow-shaped, fretted, fringed, cleft, furrowed, serrated, sinuated, in whorls, in tufts, in spires, in wreaths, endlessly expressive, deceptive, fantastic, never the same from footstalk to blossom, they seem perpetually to tempt our watchfulness and take delight in outstripping our wonder."

Now, why is this marvellous variety, this inexhaustible treasury of beautiful forms? Does it result from some innate tendency of each species? Is it intentionally designed to delight the eye of man? or has the form, and size, and texture, some reference to the structure and organization, the habits and requirements, of the whole plant?

I do not propose now to discuss any of the more unusual and abnormal forms of leaves: the pitchers of Nepenthes or Cephalotus, the pitfalls of Sarracenia or Darlingtonia, the spring-trap leaves of Dionæa, the scarcely less effective though less striking contrivances in our own Drosera or Pinguicula, nor the remarkable power of movement which many leaves present, whether in response to an external stimulus, as in certain species of Mimosa, Oxalis, &c., or as a spontaneous periodic movement, such as the "sleep"