The Brain-Power of Plants.

New Zealand Mail, Issue 915, 13 September 1889, Page 9

The Brain-Power of Plants.

(Arthur Smith, in the * National Review.’)

The modern student of plant life no longer regards the objects of his Study as so many things which demand classification and arrangement, and whose history is exhausted when a couple of Latin or Greek names have been appended to each specimen. On the contrary, the botanist of to-day seeks to unravel the mysteries of plant life. For him the plant is no longer an inanimate being, but stands revealed as ah organism exhibiting animal functions, such as breathing, circulation of blood or sap, various complex movements, and sleeping, which are as certainly equally well defined as are the analogous traits in the existence of the animal. We have seen that all these functions in the animal kingdom cannot be performed except by the agency of various nerves, &0., and that there must be a source of power behind the different nerve cells of which the brain is composed. The brain itself can, therefore, be looked upon as an intermediate motion which serves only for the more perfect transmission of impulse. This motor is absent in plants ; but does it necessarily follow that the power of force itself is non existent ? Certainly not. • There is any amount of evidence to the contrary. Some say that this power is merely instinct; but instinct, a great authority tells us, is only blind habit or automatically carried out action. If this is so, then instinotive actions only move in one direction, and cannot adapt themselves to circumstances, and have many movements and traits that are the very reverse of automatic. Numerous instances might be pointed out, in which, not only are the signs of sensibility as fully developed in the plant as in the animal, but, as I have before hinted, many phases of animal life are exactly imitated. Take for example those wonderful plants the Mimosa, sensitive of the most delicate touch.

The manner in which this plant olosea its stalks and leaves at the approach of darkness is very interesting. As the gloaming gently falls, the leaves move upwards towards each other till they touch ; the secondary leaf-stalks slowly droop till they are nearly parallel with the main leaf-stalke, which, in their turn, fall till they point to the ground. Thus it folds itself at the clo=e of day, and there is no doubt, if it were not allowed to sleep. It would, like ourselves, soon die. This is nob ouly an example of the necessity of sleep for the repairing of nervous energy and recuperation of brainpower, but a proof of the existence of the same in the vegetable kingdom. Then there are the carnivorous plants, the Venus fly-trap (Dionce), for instance, which will digest raw heef as readily “as ils insect prey. From glands with which its leaf is provided, fluids are pourel out which resemble the gastric juice of the animal stomach in its digestive properties. The matter of the insect body or inept is thus absorbed into tho substance and tissues of the plant just as the food taken into the animal stomach is digested and becomes part cf the animal fabric. In tho animal, digestion can only be commenced by tho brain-force acting by means of a nerve upon the gastric glands ; we may, therefore, concede that it is the action of the same power in the plant that produces the same effect. There is no structure in plants, so far aB its functions are concerned, more wonderful than the tip of the radicle. The course pursued by the radicle in penetrating the ground must be determined by the tip. Darwin wrote :—‘lt is hardly an exaggeration to say that the tip of the radicle, endowed, as it is, with such diverse kinds of sensitiveness, acts like the brain of animals. The brain, being seated within the extreme end of the body, receiving impressions from the sense organs, and directing the several movements.’ I do not quite agree with this, but 1 believe it to be another example of that brain-power which is the cause of all plant movement. In the commencement of plant life we find, in the case of the pea or bean, for example, the radicle emerges at one end of the seed, and the plumule at the other. Wb&t causes the radicle to descend

and the other to ascend ? If the seed is so placed that the radicle comes out at the top the result is the same, for the radicle immediately turns round and grows downwards. It cannot be gravitation, although Darwin thought it was, because that would have the same effect upon tho plumule. There can only be one reason, and that is the existence of a directing force, or brain-power, A still more remarkable inst3uce of intelligent plant movement is found in ore of the lowest forms of the vegetable kingdom, viz., the Peronospora infestans, the well-known potato fungus. I need not go into the lifehistory of this plant, it being more especially in the spores that tho existence of a power of movement according to circumstances is marked. When the spore-cases burst, a multitude of little bodies escape ; if these bodies gain access to water, they develop a couple of little tails, and by means of these tails they swim about after the mauner of tadpoles. Surely this is something higher than a mere automatic or instinctive movement. ’

There is another trait which plants have in common with animals, viz., friendship, or, as it is called, symbiosis. A sort of sympathy between certain plants has long been observed to exist, as if one loved the shadow of the other. The old Italian botanist, Malthiolus, observing some curious sympathies in plant-life, termed the phenomena * the friendship of plants.’ In his work he says :—There is so much affection between the reed and the asparagus that if we plant them together both will prosper marvellously.’ The limits of an article of thiß kind will not permit mo to go any further into this interesting subject, or to adduce more of the many other examples pointing to the fact that brain-power can and does exiat apart from a visible brain, which in the vegetable kingdom has its counterpart in that protoplasm, which, by the aid of the microscope, is seen to run hither and thither through the cells of the plant, and active movements are seen to pervade their entire organism. Vital activity is the rale, and inertness the exception in plant life; and this fact serves to impress upon us the error of that form of argument which would assume the non-existence of the highetraits of life in plants, simply because the motive-power is invisible. In contusion, I would add that, although I claim that this brain-power exists to a greater or less degree throughout the entire oreation, I do nob intend to convey the meaning that it is equal to the human understanding. Man’s intelligent will seems best to account for the progreasivenesa of the human race, wliicli so evidently marks an unsurmountable distinction between the genus homo and the rest of creation, but which would bo inexplicable were there no other difference but in the degree of their intellectual faculties, or in the quality of their brain-power. The human understanding differs from this brain-power in its being enlightened by reason, and that the principles which actuate man’s ultimate ends are best named ideas.