THE WILL IN NATURE.
unless we also assume the existence of an inner natural disposition, susceptible of being roused, which differs from the mere mechanical force in inorganic bodies… Decandolle made some remarkable experiments that proved to him the existence of a sort of habit in plants which may be overcome by artificial light, but only after a certain time. Plants that had been shut up in a cellar which was continually lit by lamps, did not on this account leave off closing in the evening and opening again in the morning for several days. And there are other habits besides which plants are able to adopt and to abandon. Flowers that habitually close in wet weather, finish by remaining open if the wet weather lasts too long. When M. Desfontaines took a sensitive plant with him in his carriage, the jolting movement at first caused it to contract, but at last it expanded again as when in complete repose. Therefore even in these cases, light, moisture, &c., &c., only act in virtue of an inner disposition, which may be neutralized or modified by the continuation of that very activity itself; and the vital energy of plants, like that of animals, is subject to fatigue and exhaustion. The hedysarum gyrans is singularly characterized by the movements of its leaves which continue day and night without needing any sort of stimulus. Surely, if any phenomenon can cause illusion and remind us of the voluntary movements of animals, it is this. Broussonet, Silvestre, Cels and Hallé have fully described it, and have shown that the plant's action depends entirely upon its own healthy condition."
Again, in the third volume of the same work, p. 166 (1828), Cuvier says: "M. Dutrochet adds some physiological considerations to which his own experiments had led him, and which in his opinion prove that the movements of plants are spontaneous, i.e. that they depend upon an inner principle which immediately receives the influence of outer agencies. As he is however reluctant to admit that plants
PHYSIOLOGY
