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Show 16 DROSERA ROTUNDIFOLIA. CHAP. I. could then be blown away by a breath of air; the leaves being thus left unencumbered and free for futuro action. Nevertheless, it often happens that all the glands do not become completel.y ~ry ; and in this case delicate objects, such as fragile Insects, are sometimes torn by the re-expansion of the tentacles into frao-ments, which remain scattered all over the leaf. Affer there-expansion is complete, the glands quickly begin to re-secrete, and as soon as full-sized drops are formed, the tentacles are ready to clasp a new object. When an .insect alights on the .central disc, it is instantly entangled by the viscid secretion, and the surrounding tentacles after a time begin to bend, and ultimately clasp it on all sides. Insects are generally killed, according to Dr. Nitschke, in about a quarter of an hour, owing to their trachere being closed by the secretion. If an insect adheres to only a f w of the glands of the exterior tentacles, these soon become inflected and carry their prey to the tentacles next succeeding them inwards; these then bend inwards, and so onwards, until the insect is ultimately carried by a curious sort of rolling movement to the centre of the leaf. Then, after an interval, the tentacles on all sides become inflected and bathe their prey with their secretion, in the same manner as if the insect had first alighted on the central disc. It is surprising how minute an insect suffices to cause this action : for instance, I have seen one of the smallest species of gnats (Culex), which had just settled with its excessively delicate feet on the glands of the outermost tentacles, and these were already beginning to curve inwards, though not a single gland had as yet touched the body of the insect. Had I not interfered, this minute gnat would CHAP. I. ACTION OF THE PARTS. 17 assuredly have been carried to the centre of the leaf and been securely clasped on all sides. We shall hereafter see what excessively small doses of certain organic fluids .and saline solutions cause strongly marked inflection. Whether insects alight on the leaves by mere chance, as a resting-place, or are attracted by the odour of the seeretion, I know not. I suspect froin the number of insects caught by the English species of Drosera, and from what I have observed with some ~xotic sp~cies kept in my greenhouse, that the odour Is attractive: In t~is latter case the leaves may be compared with a baited trap; in the former case with a trap .laid in a run frequented by game, but without any ·bait. That the ~lands pos~ess the power of absorption, is shown by their almost Instantaneously becomino- darkcoloure~ when given a minute quantity of carbo0nate of a:mmonia; the chang: of colour being chiefly or exclusively due t? the rapid aggregation of their contents. When certain o~her fluids are added, they become palecoloured. Theu power of absorption is, however, best shown by the widely different results which follow f1~0In placing drops of various nitrogenous and non~ n~trogen?us fluids of .the same density on the glands o~ the disc, or on a single marginal gland; and likeWise by the very di.ffe~·ent lengths of time during which the tentacles ~emain Inflected over objects, which yield or do not yield soluble nitrogenous matter. This same conclusion might indeed have been inferred from the str~cture and movements of the leaves, which are so adinuably adapted for capturing insects. . ~rhe absorption of animal matter from captured Insects explain~ hQ~ Drosera can flourish in extremely poor peaty soll,-In some cases where nothing but c |