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Show 278 DROSERA ANGLICA. CHAP. XII. CHAPTER XII. ON THE STRUCTURE AND MoVEMENTS OF SOME OTHER SPECIES OF DROSERA. Drosera anglica- Drosera intermedia- Drosera capensis-Drosera SlJathulata- Drosera filiform is- Drosera binata- Concluding remarks. I EXAMINED six other species of Drosera, some of thmn inhabitants of distant countries, chiefly for the sake of ascertaining whether they caught insects. This seen1ed the 1nore necessary as the leaves of some of the species differ to an extraordinary degree in shape from the rounded ones of Drosera rotundifolia. In functional powers, however, they differ very little. Drosera anglica (Hudson). *-The leaves of this species, which was sent to me from Ireland, are much elongated, and gradually widen from the footstalk to the bluntly pointed apex. They stand almost erect, and their blades sometimes exceed l inch in length, whilst their breadth is only the t of an inch. The glands of all the tentacles have the same structure, so that the extreme marginal ones do not differ from the others, as in the case of Dr·osera rotundifolia. When they are irritated by being roughly touched, or by the pressure of minute inorganic particles, or by contact with animal matter, or by the absorption of carbonate of ammonia, the tentacles become inflected· the basal portion being the chief seat of movement. Cutting o'r pricking the blade of the leaf did not exeite any movement. They frequently capture insects, and the glands of the inflected tentacles pour forth much acid secretion. Bits of roast meat were placed on some glands, and the tentacles began to move in 1 m. or * Mrs. Treat has given an excellent account in' The American Naturalist,' December 1873,p.705, of Drosera long1jolia (which is a synonym in part of Drosera anglica), of Drosera rotundifolia and filiform is. CHAP. XII. DROSERA CAPENSIS. 279 1 m. 30 s.; and in 1 hr. 10 m. reached the centre. Two bits of boiled cork, one of boiled. thread, and two of coal-cinders taken from the fire, were placed, by the aid of an instrument which had been immersed in boiling water, on five glands; those superfluous precautions having been taken on account of M. Ziegler's statements. One of the particles of cinder caused some inflection .in 8 hrs. 45 m., as did afier 23 hrs. the other particle of cinder, the bit of thread, and both bits of cork. Three glands were 'touched half a dozen times with a needle; one of the tentacles became well inflected in 17m., andre-expanded after 24 hrs.; the two oth€rs never moved. The homogeneous fluid within the cells .of the tentacles undergoes aggregation.after these have become inflected; especially if given a solution of carbonate of ammonia; and I observed the usual movements in the masses of protoplasm. In one case, aggregation ensued in l hr. 10m. after a tentacle had carried a bit of meat to the centre. From these facts it is clear that the tentacles of Drosera anglica behave like those Of flrosera 'I'Otundijolia. If an insect is placed on the central glands, or has been naturally caught there, the apex of the le<l.f curls inwards. For instance, dead flies were placed on three leaves near their bases, and after 24 hrs. the previously straight apices were curled completely over, so as to embrace and conceal the flies; they had therefore moved through an angle of 180°. After three days the apex of one leaf, together with the tentacles, began to ro-expand. But as far as I have seen-and I made many trials-the sides of the leaf are never inflected, and this is the one functional difference between this species and Drosera rotund~/olia. Drosera intermed/a (Hayne).-This species is quite as common in some parts of England as Drosera Totandifolia. It differs from Drosera anglica, as far as the leaves are concerned, only in their smaller size, and in their tips being generally a little reflexed. They capture a large number of insects. The tentacles are excited into movement by all the causes above specified; and aggregation ensues, with movement of the protoplasmic masses. I have seen, through a lens, a tentacle beginning to bend in less than a minute after a particle of raw meat had been placed on the gland. The apex of the leaf curls over an exciting object as in the case of Dr·osera anylica. Acid secretion is copiously poured over captured insects. A leaf which had embraced a fly with all its tentacles re-expanded after nearly three days. Drosera capensis.-This species, a native of the Capo of Good Hope, was sent to me by Dr. Hooker. The leaves are elongated, slightly concave along the middle and taper towards the apex, |
