Page:Popular Science Monthly Volume 47.djvu/236

226 spontaneous movements), and a low form of sensation, which he supposes might be accompanied by a degree of consciousness—"and as sensation does exist in animals independently of those eminent attributes with which it is combined in our natures as rational agents, may we not reasonably infer that vegetables have likewise their share of sensitive power, and consequently the means of enjoying their existence?" Hence, as vegetables are necessarily so different from animals in their mode of existence, it is very evident that we can not form any idea how they feel under any circumstances; but we are not on this account to conclude that they are destitute of every kind of sensation. "As they possess life, irritability, and motion, spontaneously directing their organs to what is natural and beneficial to them, and flourishing according to their success in satisfying their wants, may not the exercise of their vital functions be attended with some degree of sensation, however low, and some consequent share of happiness? (Vide Smith's Introduction to Botany.)"

Biological literature even in recent years abounds in expressions concerning phenomena of plant life corresponding to the sensorial action of animals. These conceptions were fostered to some degree by Charles Darwin's Power of Movement in Plants and other works, in which the actions of plants are described in terms strictly applicable to the sensorial reactions of animals only. Thus he says of the irritability of the tips of roots, "It is hardly an exaggeration to say that the tips of the roots affected and having the power of directing movement in the adjoining parts act like the brain of the lower animals." This phraseology was, no doubt, intended to be suggestive rather than definitive, but to it may be traced many current erroneous impressions. "Instinct," "intelligence," "nervous action," and a score of similar terms are used indiscriminately to designate actions of plants far removed in character from those denoted by the original meaning of such expressions. A partial justification of this misapplication of terms is found in the lack of systematically arranged information concerning the form of sensibility exhibited by plants. With an extensive nomenclature dealing with the great mass of detail of the neuro-muscular action of animals at command, the apparent similarity between the irritation reactions of plants and the sensorial reactions of animals has been held to be real, in a manner strongly suggestive of the anecdote of the German peasant who, seeing a moving locomotive for the first time, exclaimed, "There's a horse inside of it, or how could it run?"

The conception of the relative character of these two great groups of reactions may be attained by outlining the conditions which have led to the development of each rather than by an accentuation of external similarities.