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Show 14 DROSERA ROTUNDJFOLIA. 0IIAJ'. l. secretion, so that when the leaves are lifteu out, long ropes of extremely viscid :fi uid hang fro:m th~m. Some acids, on the other hand, do not act In this manner. Increased secretion is not necessarily d pendent on the inflec.tion of the tentacle, for particles of sugar and of sulphate of zinc cause no movement. It is a much more remarkable fact that when an object, such as a bit of meat or an insect,. is placed on the disc of a leaf, as soon as the surrounding tentacles become considerably inflected, their glands pour forth . an increased amount of secretion. I ascertained this by selectino- leaves with equal-sized drops on the two sides, and by placing bits of meat on one side of the disc· and as soon as the tentacles on this sid became much' inflected, but before the glands touched the meat, the drops of secretion became larger. This was repeatedly observed, but a record was kept of only thirteen cases, in nine of which increased secretion was plainly observed ; the four failures being due either to the leaves being rather torpid, or to the bits of meat being too small to cause much inflection. We must therefore conclude that the central glands, when strongly excited, transmit some influence to the glands of the circumferential tentacles, causing them to secrete more copiously. It is a still more important fact (as we shall see more fully when we treat of the digestive power of ' the secretion) that when the tentacles become inflected, owing to the central glands having been stimulated mechanically, or by contact with animal matter, the secretion not only increases in quantity, but changes its nature and becomes acid; and this occurs before the glands have touched the object on the centre of the leaf. This acid is of a different nature from that contained in the tissue of the leaves. As long as the CHAP. I. AC'riON OF THE r ARTS. 15 tentacles remain closely inflected, the glands continue to s.e crete, and the secretion is acid ,· so that, 1'f neu-tr. ahsed by carbonate of soda, it again becomes acid after a few hours. I have observed the same leaf with the tentacles closely inflected over rather indigestible s. ubstances, s. uch as c. hemicall. y prepared case1·n , pour- Ing forth acid secretion for e1ght successive day d b. f s, an ove~· Its o ~one for ten successive days. 1 he s~cretion ~eems to possess, like the gastric juice of the higher animals, some antiseptic power. During v_ery w~rm weather I placed close together two equalsized bits of raw meat, one on a leaf of the Drosera and the other surrounded by wet moss. They wer~ thus left for 48 hrs., and then examined. The bit on the moss swarmed with infusoria, a~d was so much rlecayed that the transverse strim on the muscular fibres could. no longer be. clearly distinguished; whilst. the bit on the le~f, which was bathed by the secretion, was free from Infusoria, and its strioo \vere perfectly distinct in the central and undissolved portion. In like manner small cuLes of albumen and cheese placed on wet moss became threaded with fi~aments of moul~,. and had their surfaces slightly discoloured and disintegrated ; whilst those on the leaves of Drosera remained clean, the albumen beinochanged in to transparent fluid. 0 . As soon a~ tentacles, which have remained closely Inflected dunn~ several days over an object, begin to re-expand, their glands secrete less freely, or cease to secrete,. and are left dry. In this state they are co~ered with a film of whitish, semi-fibrous matter w h1?h was held in solution by the secretion. Th~ ~ryi~g of the glands during the act of re-expanSion Is of some little service to the plant; for I have often observed that objects adhering to the leaves |