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Show 300 DION lEA MUSCIPULA. CHAP. XIII. well aggregated. Aggregation may be seen to occur very quickly if a piece of a leaf is immersed in a w ak solution of carbonate of am1nonia. Again, · small cubes of albumen and gelatine were left for eight days on a leaf, which was then cut open. The whole surface was bathed with acid secretion, and every cell in the many glands which wore examined had its contents aggregated. in a beautiful manner into dark or pale purple, or colourless globular masses of protoplasm. These underwent incessant slow changes of fonns ; sometimes separating from one another and then reuniting, exactly as in the cells of Drosera. Boiling water makes the contents of the gland-cells white and opaque, but not so purely white and porcelain-like as in the case of Drosera. How living insects, when naturally caught, excite the glands to secrete so quickly as they do, I know not; but I suppose that the great pressure to which they are subjected forces a little excretion from either extremity of their bodies, and we have seen that an extremely small amount of nitrogenous matter is sufficient to excite the glands. Before passing on to the subject of digestion, I rna y state that I endeavoured to discover, with no success, the functions of the minute octo:fid processes wit~ which the leaves are studded. From facts hereafter to be given in the chapters on Aldrovanda and lTtricularia, it seemed probable that they served to absorb decayed matter left by the captured insects; but their position on the backs of the leaves and on the footstalks rendered this almost impossible. Nevertheless, leaves were immersed in a solution of one part of urea to 437 of water, and after 24 hrs. the orange layer of protoplasm within the arms of these processes did not appear more aggregated than in other speci- CHAP. XIII. DIGESTION. 301 mens kept in water. I then tried suspending a leaf in a bottle over an excessively putrid infusion of raw meat, to see whether they absorbed the vapour, but their contents were not affected. D?:gestive Power ojthe Secretion.*-When a leaf closes over any object, it may be said to form itself into a temporary stomach; and if the object yields ever so little animal rna tter, this serves, to use Schiff's expression, as a peptogene, and the glands on the surface pour forth their acid secretion, which acts like the gastric juice of ani1nals. As so many experiments were tried on the digestive power of Drosera, only a few were made with Dionrea, but they were amply sufficient to prove that it digests. This plant, moreover, is not so well fitted as Drosera for observation, as the process goes on within the closed lobes. Insects, even beetles, after being subjected to the secretion for several days, are surprisingly softened, though their chitinous coats are not corroded. Expen'ment 1.-A cube of albumen of To of an inch (2·544 mm.) was placed at one end of a leaf, and at the other end an oblong piece of gelatine, t of an jnch (5·08 mm.) long, and * Dr. W. M. Canby, of Wilmington, to whom I am much indebted for information regarding Dionroa in its native homo, has published in the' Gardener's Monthly,' Philadelphia, August 1868, some interesting observations. He ascertained that tho secretion digests animal matter, such as the contents of insects, bits of moat, &c.; and that the secretion is reabsorbed. He was also well aware that the lobes remain closed for a much lono-er time when in contact with ani~al matter than when made to shut by a mere touch, or over objects not yielding soluble nutriment; and that in those latter cases the glands do not som·eto. The Rev. Dr. Curtis first observed(' Boston Journal Nat. Hist.' vol. i. p. 123) tho secretion from the g-lands. I may here add that a gardener, Mr. Knight, is aiu (Kirby and Spencer's 'Introduction to Entomology,' 1818, vol. i. p. 295) to have found that a plant of the J Homea, on the leaves of which "he laid fine filaments of mw beef, ·was much more luxuriant in its growth than others not so treated." |
