Plant Physiology

Summary

The corroborations I have to cite concerning the appearance of will in plants come primarily from the French, a nation with a decidedly empirical bent, not wanting to go a single step beyond that which is immediately given. Moreover the one reporting the information, Cuvier, by insisting on the purely empirical, gave occasion for the famous dispute between himself and Geoffroy St Hilaire. Thus it should not surprise us if here we do not encounter such definite language as in the German evidence cited earlier and if we see every concession made with cautious reserve.

In his History of the Progress of Natural Science from 1789 to the Present, Vol. 1 (1826), Cuvier says, p. 245: ‘Plants have certain apparently spontaneous (spontanés) movements that they show under certain circumstances and that are sometimes similar to those of animals, so that on account of this, a kind of sensation and will might be attributed to plants, which might be done especially by those who want to see a similarity to the movements of the internal parts of animals. In this way the tops of trees always tend toward the vertical, except when they incline toward the light. Their roots reach for rich soil and moisture and deviate from a straight path to find these. But these various directions are not explicable from the influence of external causes unless an inner natural tendency is assumed, one which is capable of being stimulated and is different from mere inertia in inorganic bodies … Decandolle has performed noteworthy experiments that indicated to him a type of tendency among plants that is overcome by artificial light only after a certain amount of time. Plants enclosed in a cellar continually lit by lamps did not cease for several days to close upon the onset of night and open in the morning. And there are even other tendencies that plants can acquire and cannot give up. Flowers that close in wet weather in the end remain open when the rain persists for too long. When Mr Desfontaines took a sensitive plant with him in a wagon, at first it contracted because of the shaking, but finally upon complete rest it re-extended.