Apart from these examples, drawn from classical works, we would ask what becomes of the argument for the immobility of plants, considered as a distinctive characteristic of the vegetable kingdom, when we see that zoophytes are fixed to the earth, and when, on the other hand, we see certain young plants, or their germs, such as the germs of algæ, mosses, and ferns, possessing the faculty of motion.
The spores, or reproductive organs of algæ, and the impregnating corpuscles of the mosses and ferns, possess the fundamental characteristics of animality, that is to say, they are provided with locomotive organs, and they execute movements which appear to be voluntary. Those singular creatures are seen to go and come in the interior of liquids, to endeavour to penetrate into cavities, to withdraw, return, and definitively introduce themselves with an apparent effort.
The German botanists regard these vegetable germs as belonging to the animal kingdom. Considering that only animals have the organs of motion, and that the spores of algæ and the impregnating corpuscles of mosses and ferns are provided with organs of motion, they do not hesitate to declare that in the commencement of their life, algæ, mosses, and ferns are in truth animals, which become plants when they fix themselves, and begin to germinate. French botanists have not yet ventured to adopt that view; they are content to call the movable impregnating corpuscles of algæ, mosses, and ferns, antherozoïdes, but they do not dare to pronounce upon their animality. M. Pouchet says, in his work L'Univers, page 444:
"Motion manifests itself spontaneously with extraordinary intensity in the animalculæ of several plants, which have spinal organs for this purpose, hairs by means of which they swim about in the liquid which contains them.
"Some of these, real animalcule plants, have the shape of eels, and move themselves by means of two long filaments attached to their heads; others exactly resemble the tadpoles of frogs, and jump about in the cells of the mosses.
"Nevertheless, it is such creatures as these, whose locomotive organs are so plainly to be discerned, and which we can see, under the microscope, jumping about as nimbly as our acrobats, that certain botanists persist in considering, on theory alone, as motionless and insensible. Some philosophers certainly possess eyes, that they may not see!"
There are these germs of plants, and young plants which move, and on the other hand, almost all the adult zoophytes, sponges, corals, madrepores, sea-stars, byssus, &c., &c., to which we may add several mollusca (all those in shells), are fixed to the earth. In these cases we must take the plant for the animal, and the animal for the plant, if we positively hold by voluntary motion as an absolute distinction between animals and plants.
On the borders of the two kingdoms,—when we consider zoophytes in the animal, and cryptogams in the vegetable kingdom,—there is no longer, so to speak, either animal or plant; the two seem to be confounded, and fused together.
If, before the discovery of the fresh-water polype, that living creature had been presented to a naturalist, he would have felt puzzled how to class it. Seeing it multiplying itself by buds, by offshoots, by engraftment, he would doubtless have declared that this organized being was a plant. But if he had been made to remark that this same creature fed on living prey, which it seized and swallowed, that it had long and flexible arms, of which it formed a kind of net for the purpose of seizing this prey, which it conveyed into the interior of a digestive tube, our naturalist would have made haste to place the polype in the ranks of the animals. He would have been asked to observe that the polype may be turned inside out, like a glove, so that his interior skin becomes his exterior skin, and that, thus turned inside out, he lives, grows, and multiplies himself, precisely as he does before this curious reversal. Our naturalist, much embarrassed in the presence of so unheard of a fact, would doubtless immediately have begun to seek some intermediate kingdom between the animal and the vegetable, to which he might relegate this paradoxical being, which could not, with absolute certainty, be classed either with plants, or with animals.
The fact is, classifications are products of human science, nature knows nothing about them. We descend, by insensible degrees, from one kingdom to the other; we go from the man to the polype, and from the polype to the rose tree, by infinite gradations, and, on the confines of the two kingdoms, there is a whole series of creatures which it is very difficult to range under any system. For how long did naturalists hesitate before they regarded infusoria, coral, sponges, star-fish, gorgons, sea-anemones, and madrepores as animals? Even in the present day micrographers who study the microscopic beings proper to vegetable and animal infusions, such as the monads, polypoid worms, and numerous others, find the utmost difficulty in assigning these creatures to such or such a kingdom, and they sometimes decide rather arbitrarily upon placing them among animals or plants.
From all the considerations, all the facts which we have just advanced, we conclude that the sensibility of plants is not to be contested, since no one can think of denying that privilege to certain zoophytes which can with difficulty be distinguished from vegetables.
We see an imposing tree, a stately oak with sturdy branches, growing on the sea coast. Not far off, on the sand of the shore, lies a star-fish flung there by the waves. A few yards below, on the surface of the water, floats a sponge, a branch of coral, a madrepore. When the icy wind blows, when the hurricane lifts the angry waves, which is it, the animal or the plant that will manifest sensibility to the tempest? The sponge, the coral, the madrepore will remain as indifferent to the fury of the elements as the rock in which they are incrusted, or as the pebble on which the star-fish stretches out its four motionless arms. But, the majestic oak will shudder at every gust of the tempest; he will bend his branches and shut up his leaves to shelter himself from the icy blast or the furious storm; and a mere glance at his attitude will indicate to you that an abnormal perturbation reigns in the atmosphere. Would you seriously say, in that case, that the vegetable feels nothing, and that the animal is sensible? Would you not, on the contrary, be inclined to declare that the tree is the sentient being, and that the star-fish, the sponge, the madrepore, are the creatures which are destitute of feeling?