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Show 54 DROSERA ROTUNDIFOLIA. CnAP. III. could be seen filled with purple flui_d, without ~ vestige of aggregated protoplasm; the whole havm.g been .redissolved. A loaf with ao-gregated masses, caused by Its having boon waved for 2 m. in ~ater at the temperature of 125° Falu., was loft in cold water and after 11 hrs. tho protoplasm showed traces of incipient redissolution. When again ~xamined thre~ days after its immersion in the warm water, there was a conspicuous difference, though the protoplasm was Rtill somewhat aggregated. Another leaf, with the contents of a.n tho cells strongly. aggregated from the action of a weak solutiOn of ~ hosph~tc of ammonia, was left for between three and four days In a mixture (known to be innocuous) of one dr~chm of alcohol to eight drachms of water, and when re-examined every trace of aggregation had disappeared, the cells being now filled with homogeneous fluid. We have seen that leaves immersed for some hours in dense solutions of sugar, gum, and starch, have the contents of their cells greatly aggregated, and are rendered more or less flacci<.l, with the tentacles irregularly contorted. These leaves, after heing left for four days in distilled water, became loss flaccid, with their tentacles partially re-expanded, and the aggregated masses of protoplasm were partially red is. ol vcd. A leaf with its tentacles closely clasped over a fly, and "\vith the contents of the cells strongly aggregated, was placed in a little sherry wine; after 2 hrs. several of the tentacles had reexpanded, and the others could by a mere touch be pu hod back into their properly expanded positions, and now all traces of aggregation had disappeared, the cells bcin()' filled with perfectly homogeneous pink fluid. The redis olution in these cases may, I presume, be attributed to endosmosc. On the Proxin~ate Causes of the Process of Aggregat~'on. As most of the stimulants which cause the inflection of the tentacles likewise induce aggregation in the eontents of their cells, this latter process n1ight be thought to be the direct result of inflection ; but this is not the case. If leaves are placed in rather strong solutions of carbonate of aminonia, for in tanco of three or four, and even sometimes of only two grains to the ounce of water (i .. one part to 109, or 146, or CHAP. III. THE PROCESS OF AGGREGATION. 55 218, of \Vater), the tentacles are paralysed, and do not beco1ne inflected,. yet they soon exhibit strongly marked aggregation. Moreover, the short centra] tentacles of a leaf which has been immersed in a w.eak solution of . any .salt of ammonia, or in any nitrogenous organic fluid, do not become in the least inflected; neverth~less they exhibit all the phenomena of aggregation. On the other hand several acids cause strongly pronounced inflection 'but no aggregati.o n. · ' It is an important fact that when an oraanic or inorganic object is placed on the glands ~f the disc anJ the exterior tentacles are thus caused to bend inwards, not only is the secretion from the ()'lands of the latter increased in quantity and rende~eJ acid but the contents of the cells of their pedicels becom~ aggregated. The process always commences in the glands, although these have not as yet touched any object. Some force or influence must, therefore b~ transmitted from the central glands to the ext~rior tentacles, first to near their bases causing this part to bend, and next to the glands causing them to secrete ~noi~e copiously. _..1\.fter a short time the glands, thus Inchrectly excited, transmit or reflect some influence down their own pedicels, inducing aggregation in cell beneath cell to their bases. . It .seems at first sight a probable view that aggregation Is due to the glands being excited to secrete more copiously, so that sufficient fluid is not left in their cells, and in the cells of the pedicels, to hold the protoplasm in solution. In favour of this view is the fact that aggregation follows the inflection of the tentacles, and during the movement the glands generally, or, as I believe, always, secrete more copiously than they did before. Again, during the re-expansion |