F. J. Meyen has devoted a chapter, entitled "Of the movements and sensations of plants," to a full investigation of the subject now before us. In this he says[251]: "Not unfrequently potatoes, stored in deep, dark cellars, may be observed towards summer to shoot forth stems which invariably grow in the direction of the chinks through which the light comes into the cellar, and to continue thus growing until they at last reach the aperture which receives the light directly. In such cases potato-stalks have been known to reach a length of twenty feet; whereas under ordinary circumstances, even such as are most favourable to the growth of the potato, the stalk is seldom longer than from three to four feet. It is interesting to watch closely the course taken by a potato-stalk thus growing in darkness, in its endeavours to reach the light. It tries to do so by the shortest road, but not being firm enough to grow straight across through the air without support, it lets itself drop on to the floor, and thus creeps along the ground till it reaches the nearest wall, up which it then climbs." Even this botanist too is led by his facts to the following assertion (p. 576): "On observing the freedom of movement of _oscillatoria_ and other inferior plants, we may perhaps have no alternative but to attribute a species of _will_ to these beings." [251] F. J. Meyen, "Neues System der Pflanzenphysiologe" (1839), vol. iii. p. 585. Creepers bear distinct evidence as to manifestation of will in plants; for, when they find no support near enough for their tendrils to cling to, they invariably direct their growth towards the shadiest place, or even towards a piece of dark-coloured paper, wherever it may be placed; whereas they avoid glass, on account of its glitter. In the "Philosophical Transactions" of 1812, Th. Andrew Knight relates some very pleasing experiments on this subject (especially with _ampelopsis quinquefolia_,)[252] although he strives hard to explain the matter mechanically, and will not admit that it is a manifestation of will. I appeal to his experiments, not to the conclusions he draws from them. A good test might be, to plant several free creepers in a circle round a tree-trunk and to observe whether they all crept towards the trunk centripetally. On the 6th Nov. 1843, Dutrochet read a treatise on this subject in the "Acad. de Sciences" called "Sur les Mouvements Révolutifs spontanés chez les Végétaux," which, notwithstanding its great length, is well worth reading, and is published among the "Comptes rendus des Séances de l'Académie des Sciences" for Nov. 1843. The result is, that in _pisum sativum_ (green pea), in _bryonia alba_ (wild bryony) and in _cucumis sativus_ (cucumber) the stems of those leaves which bear the tendrils, describe a very slow circular movement in the air, the time in which they complete an ellipsis varying from one to three hours according to temperature. By this movement they seek