THE WILL IN NATURE.
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 Académie des Sciences called "Sur les Mouvements Révolutifs spontanés chez les Végétaux," which, notwithstanding its great length, is well worth reading, and is published among the Compte rendu 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 at random for solid bodies round which, when found, they twine their tendrils; these then support the plant, it being unable to stand by itself without help. That is, they do the same thing as the eyeless caterpillar, which when seeking a leaf describes circles in the air with the upper part of its body. Dutrochet contributes a good deal of information too concerning other movements in plants in this treatise: for instance, that stylidium graminifolium in New Holland, has a column in the middle of its corolla which bears the anthers and stigma and alternately folds up and unfolds again. What Treviranus adduces is to the same effect: 1 "In parnassia palustris and in ruta graveolens, the stamina incline one after the other, in saxifraga tridactylites in pairs, towards the stigma, and erect themselves again in the same order." Shortly before however, we read in Treviranus with reference to this subject: "Of all apparently voluntary movements of plants, the direction of their boughs and of the upper surface of their leaves towards the light and towards moist heat, and the twining
1 Treviranus, Die Erscheinungen und Gesetze des Organischen Lebens (Phenomena and Laws of Organic Life), vol. i. p. 173.
PHYSIOLOGY
