* Since his original publication, Stein has found out that the irritability of the leaves was observed by De Sassus, as recorded in ‘Bull. Bot. Soc. de France,’ in 1861. Delpino states in a paper published in 1871 (‘Nuovo Giornale Bot. Ital.’ vol. iii. p. 174) that “una quantit di chioccioline e di altri animalcoli acquatici” are caught and suffocated by the leaves. I presume that chioccioline are fresh-water molluscs. It would be interesting to know whether their shells are at all corroded by the acid of the digestive secretion. ** I am greatly indebted to this distinguished naturalist for having sent me a copy of his memoir on Aldrovanda, before its publication in his ‘Beiträge zur Biologie der Pflanzen,’ drittes Heft, 1875, page 71. [page 322] taining numerous crustaceans of the genus Cypris, and next morning many were found imprisoned and alive, still swimming about within the closed leaves, but doomed to certain death. Directly after reading Prof. Cohn’s memoir, I received through the kindness of Dr. Hooker living plants from Germany. As I can add nothing to Prof. Cohn’s excellent description, I will give only two illustrations, one of a whorl of leaves copied from his work, and the other of a leaf pressed flat open, drawn by my son Francis. I will, however, append a few remarks on the differences between this plant and Dionaea. Aldrovanda is destitute of roots and floats freely in the water. The leaves are arranged in whorls round the stem. Their broad petioles terminate in from four to six rigid projections,* each tipped with a stiff, short bristle. The bilobed leaf, with the midrib likewise tipped with a bristle, stands in the midst of these projections, and is evidently defended by them. The lobes are formed of very delicate tissue, so as to be translucent; they open, according to Cohn, about as much as the two valves of a living mussel-shell, therefore even less than the lobes of Dionaea; and this must make the capture of aquatic animals more easy. The outside of the leaves and the petioles are covered with minute two-armed papillae, evidently answering to the eight-rayed papillae of Dionaea. Each lobe rather exceeds a semi-circle in convexity, and consists of two very different concentric portions; the inner and lesser portion, or that next to the midrib, * There has been much discussion by botanists on the homological nature of these projections. Dr. Nitschke (‘Bot. Zeitung,’ 1861, p. 146) believes that they correspond with the fimbriated scale-like bodies found at the bases of the petioles of Drosera. [page 323] is slightly concave, and is formed, according to Cohn, of three layers of cells. Its upper surface is studded with colourless glands like, but more simple than, those of Dionaea; they are supported on distinct footstalks, consisting of two rows of cells. The outer FIG. 13. (Aldrovanda vesiculosa.) Upper figure, whorl of leaves (from Prof. Cohn). Lower figure, leaf pressed flat open and greatly enlarged.