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Show DROSERA HOTUNDIFOLIA. CHAP. III. effect may be attributed to exosmose ~ for the loaves in tho syrup became quite flaccid, and those In t~e gum and .starch Romewhat flaccid, with their tentaeleR t~v1sted about 1n the most irregular manner, the longer ones l1 ke corlmcrews. We Hhall hereafter see that solutions of these substances, when placed on the discs of leaves, do not in~ite inflection. ParLicles of soft sugar were added to t~e secretiOn .round sev~ral glands and were soon dissolved, causmg a great Increase of the secretion, no doubt by exosmose; and after 24 hrs. the cells showed a certain amount of aggregation, though the tentacles were not inflected. Glycerine causes in a few minutes well -pronounced aggregation, commencing as u. ·ual within the glands and then travelling down the tentacles; and this I presume may be attributed to the strong attracti?n of this substance ftn· water. Immersion for several hours 1n water causes some degree of aggregation. Twenty leav?s were first . carefully examined, and re-examined after having been left ImmerRed in distilled water for various periods, with the following resnltR. It is rare to find even a trace of aggregation until 4 or 5 and generally not untH several more hours have elapsed. When however a leaf becomes quickly inflected in water, as sometimes happens, especially during very warm weather, aggregation may occur in little over 1 hr. In all cases leaves left in water for more than 24 hrs. have their glands blackened, which ~hows that their contents are aggregated; and in the specimens which were carefully examined, there was fairly well-marked aggregation in tho upper cell. of the pedicels. 'rhese trials were made with cut-off leaves, and it occurred to me that this circumstance might influence the rc~sult, as the footstalks would not perhaps absorb water qui ckly enough to supply the glands as they conbnned to secrete. But this view was proved erroneous, for a plant with uninjured roots, bearjng fonr leaves, was submerged in eli tilled water for 47 hrs., and the glands w0re blackened, though the t entacles were very little inflected. In one of these leaves there was only a sUght degree of aggregation in the tentacles; in the econd rather more, the purple contents of the cells being a little separated from the walls; in the third and fourth, which were pale leaves, the aggregation in the upper parts of the pedice]s was well marked. In these leaves tho little masses of protoplasm, many of which were oval, slowly changed their forms and positions; so that a submergence for 47 hrs. had not killed the protoplasm. In a previous trial with a submerged plant, the tentacles were not in the least inflected. CHAP. III. THE PROCESS OF AGGREGATION. Heat induce_s . aggregation. A leaf, with the cells of the tentacles contaming only homogeneous fluid was waved about for 1 m. in water at 130° Fahr. (54°·4 Ce~t.), and was then ~xa~ined under the microscppe as quickly as possible, that Is In 2 m. or 3 m.; and by this time the contents of the cells had undergone some degree of aggregation. A second leaf was :vaved for 2 _m. in water at 125° (51°·6 Cent.) and quickly examined as before; the tentacles wore well inflected· th(' purple flu_id in all the. cells had shrunk a little from the ~ails: a~d con~amed. many oval and elongated masses of protoplasm, with a few mrnute spheres. A third leaf was left in water at ~25°, until it cooled, and when examined after 1 hr. 45 m., the Inflected tentacles showed some aggregation, which became ~fter 3 hrs. more stron?ly marked, but did not subsequently Increase. Lastly, a leaf was waved for 1 m. in water at 1201 (48°·8 Cent.) and then left for 1 hr. :26 m. in cold water· the tentacles were but little inflected, and there was only her~ an<l there a trace of aggregation. In all these and other t1·ials with warm w~ter the p~otoplasm showed much less tendency to aggregate Into sphencal masses than when excited by carbonate of ammonia. Redissolution of the Agg1·egated Masses of Protoplasm.-As soon as. tentacles which _have clasped an insect or any inorganic obJect, or have been 111 any way excited, have fully re-expanded, the aggregated masses of protoplasm are redissolved and disap~ ear; the cells being now refilled with homogeneous purple tlu1d as they were before the tentacles were inflected. The process of redissolution in all cases commences at the bases of the tentacles, and proceeds up them towards the glands. In old leaves, however, especially in those which have been several times in action, the protoplasm in the uppermost cells of the p~~icels remains in a permanently more or less aggregated conditiOn. In order to observe the process of redissolution the following observations were made: a leaf was left for 24 h;.R. in a little solution of one part of carbonate of ammonia to 218 of water, and the protoplasm was as usual aggregated into numberJess purple spheres, which were incessantly changing their forms. The leaf was then washed and placed in distilled water, and_ after 3 hrs. 15 m. some few of the spheres began to show by thmr less clearly defined edges signs of redissolution. After 9 hrs. many of them had become elongated, and the surrounding_ fluid in the cells was slightly more coloured, showing plainly that redissolution had commenced. After 24 hrs., though many cells still contained spheres, here and there ont> |