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Show 42 DROSERA ROTUNDIFOLIA. CHAP. III. • unication between the two. On the channel of dcommh connecting threads are some-the other han '~~c 1 and th ir extremities then times seen to lreba hr, aded The other sketches in uickl y become c u - e : ~o-. 8 show the forms successive.ly a~su~ed. . b hortl after the purple fhud within the cells. has S y . ated the little masses float about In a ~:f~=~e:Sg~~e~lmo~t colourless fi~id; and the layer of wh.i te granu1 a r pr· otoplasin which flo. w.s al1o ng Tthhe walls can now b e seen much more distinct y.1 1 de t. m flows at an irregular rate, up one wa an sd oJwean t h e opposi" te one ' generally at a slower dr ate across the narrow ends of the elongated c. lls, an so round and round. But the current som tlmc.s ceasets. The movemen t I.S often in waves' and thou . .cressf sometimes stretch almost across the whole width o the cell and then sink down again. Small sp~ res of protopl~sin, apparently quite free, are oft n dnven by t h e curren t roun d the Cells.' and filam nts attache·df to the central masses are swayed to and fro, as 1 struggling to escape. Altogether, one of th ~e c ~ls with the ever changing c ntral masses, and with t le layer of protoplasm flowing round the walls, presents a wonderful scene of vital activity. Many observations were made on the contents of the c~ll·~ whilst undergoing the process of aggregation, but I sh~ll de:~ only a few cases under different heads. A small portwn 1 ° d leaf was cut off·, placed under a high power, and the. ~· antis very gently pressed under a compresr:;or. In 15m. I ~1s ~~~:saw extremely minute spheres of pr~topl~sm aggre~atn:g b th selves in the purple fluid; these rapidly Increased In ~Ize, f ~h within the cells of the glands and of the upper en s 0 ~ pedicels Particles of glass, cork, and cinders were also place on the ~lands of many tentacles; in 1 hr. several of. them w~:~ inflected but after 1 hr. 35m. there was no aggregatiOn. Ot d tentacle; with' these particles were examined after 8 hrs., an CHAP. III. THE PROCESS OF AGGREGATION. 43 now all their cells had undergone aggregation; so had the cells of the exterior tentacles which had become inflected through the irritation transmitted from the glands of the disc, on which the transported particles rested. This was likewise the case with the short tentacles round the margins of the disc, which had not as yet become inflected. This latter fact shows that the process of aggregation is independent of the inflection of the tentacles, of which indeed we have other and abundant evidence. Again, the exterior tentacles on three leaves were carefully examined, and found to contain only homogeneous purple fluid; little bits of thread were then placed on the glands of three of them, and after 22 hrs. the purple fluid in their cells almost down to their bases was aggregated into innumerable, spherical, elongated, or filamentous masses of protoplasm. The bits of thread had been carried some time previously to the central disc, and this had caused all the other tentacles to become somewhat inflected; and their cells had likewise undergone aggregation, which however, it should be observed, had not as yet extended down ·to their bases, but was confined to the cells close beneath the glands. Not only do repeated touches on the glands* and the contact of minute particles cause aggregation, but if glands, without being themselves injured, are cut off from the summits of the pedicels, this induces a moderate amount of aggregation in the headless tentacles, after they have become inflected. On the other hand, if glands are suddenly crushed between pincers, as was tried in six cases, the tentacles seem paralysed by so great a shock, for they neither become inflected nor exhibit any signs of aggregation. Uarbonate of .Ammonia.-Of all the causes inducing aggregation, that which, as far as I have seen, acts the quickest, and is the most powerful, is a solution of carbonate of ammonia. Whatever its strength may be, the glands are always affected first, and soon become quite opaque, so as to appear black. For instance, I placed a leaf in a few drops of a strong solution, namely, of one part to 146 of water (or 3 grs. to 1 oz.), and observed it under a high power. All the glands began to * Judging from an account of M. Heckel's observations, which I have only just seen quoted in the 'Gardener's Chronicle' (Oct. 10, 1874), he appears to have observed a similar phenomenon in the stamens of Berberis, after they have been excited by a touch and have moved; for he says, "the contents of each individual cell are collected together in the centre of the cavity." |