In the "Mém. de l'Acad. d. Sciences de l'année" (1821), Cuvier says[249]:--"For centuries botanists have been searching for the reason why in a seed which is germinating the root invariably grows downwards, while the stalk as invariably grows upwards, no matter what be the position in which the seed is placed. M. Dutrochet put some seeds into holes bored in the bottom of a vessel filled with damp mould, which he hung up to a beam in his room. Now, in this case, the stem might have been expected to grow downwards. Not at all: the roots found their way to the air below, and the stems were prolonged so as to traverse the damp mould until they reached its upper surface. According to M. Dutrochet, the direction in which plants grow, is determined by an inner principle and not at all by the attraction of the bodies towards which they direct themselves. A mistletoe seed that was fastened to the point of a perfectly moveable needle fixed on a peg, with a small plank placed near it, was induced to germinate. It soon began to send out shoots towards the plank, which it reached in five days without having communicated the slightest movement to the needle. The stems of onions and leeks with their bulbs, deposited in dark places, grow upwards, although more slowly than in light ones; they grow upwards even if placed in water: a fact which suffices to prove that neither light nor moisture determines the direction of their growth."--Still C. H. Schultz asserts[250] that he made seeds germinate in a dark box with holes bored in the bottom, and succeeded in inducing the plants to grow upside down, by means of a mirror fastened to the box, which reflected the sunlight. [249] Vol. v. p. 171. Paris, 1826. [250] C. H. Schultz, "Sur la Circulation dans les Plantes," a prize-essay, 1839. In the "Dictionnaire des Sciences Naturelles" (article _Animal_) we find: "If, on the one hand, animals show avidity in their search after nourishment as well as power of discrimination in the selection of it, roots of plants may, on the other hand, be observed to direct themselves towards the side where the soil contains most nourishment, nay, even to seek out the smallest crevices in rocks which may contain any food. If we twist a bough so as to make the upper surface of its leaves the under one, these leaves even will twist their stems in order to regain the position best suited for the exercise of their functions (_i.e._ so as to have the smooth side uppermost). Is it quite certain that this takes place unconsciously?"