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Show 78 DROSERA ROTUNDIFOLIA. CHAP. V. 30 hrs. Inflection was never th.us ca u~ed. It is. necessary to try pure gum arabic, for a friend tried a solutiOn bought ready prepared, and this cau.sed the .tentacles to b?nd; but he afterwards ascertained that It contmned much animal matter, probably glue. . . Sug(J,r.-Drops of a solutwn of white sugar of three strengths (the weakest containing one part of sugar to 73 of water) were left on fourteen leaves from 32 hrs. to 48 hrs.; ~ut no effect waH produced. . Starch.-A mixture about as thiCk as cream was dropped on six leaves and left on them for 30 hrs., no effect being produced. I am Sl;lrprised at this fact, as I believe that the s~arc~1 of commerce generally contains a trace of gluten, and tlns nitrogenoui-> substance causes inflection, as we shall see in the next chapter. Alcohol, Diluted.-One part of alcohol was added to seven of water, and the usual drops were placed on the dif::CS of three leaves. No inflection ensued in the courRe of 48 hrs. To a. ·certain whether these leaves had been at all injured, hits of meat were placed on them, and after 24 hrs. they were clo ely inflected. I also put drops of sherry-wine on three other leaves; no inflection was caused, though two of them seemed omewhat injured. We shall hereafter see that cut-off leaves in1mer ed in diluted alcohol of the above strength do not become inflected. OUve Uil.-Drops were placed on the discs of eleven leaves, and no effect was produced in from 24 hrs. to 48 hrs. Four of these leaves were then tested by bits of meat on their di es, and threo of them were found after 24 hrs. with all their tentacles and blades closely inflected, whilst tho fourth had only a few tentacles inflected. It will, however, be shown in a future place, that cut· off leaves immersed in olive oil are powerfully affected. lrifusion and Decoction of Tea.-Drops of a strong infusion and decoction, as well as of a rather weak decoction, of tea were placed on ten leaves, none of which became inflecteJ. I afterwards tested three of them by adding bits of meat to the drops which still remained on their discs, and when I examined them after 24 hrs. they were closely inflected. The chemi al principle of tea, namely theine, was subsequently tried and produced no effect. The albuminous matter which the leaves must originally have contained, no doubt, had been rendered insoluble by their having been completely qried. We thus see that, excluding the experi1n nts with water, sixty-one leaves were tried with drops of the CHAP. v. EFFECTS OF ORGANIC FLUIDS. 79 above-named non-nitrogenous fluids; and the tentacles were not in a single case inflected. With respect to nitrogenous fluids, the first which came to hand were tried. The experiments were made at the same tim~ and .in ex~ctly the. same manner as the foregoing. As It was Immediately evident that these fluids produced a great effect., I neglected in most cases to record how soon tho tentacles became inflected. But this always occurred in less than 24 hrs.; whilst the drops of non-nitrogenous fluids which produced no effect were observed in every case during a considerably longer period. Mil/c.-Drops were placed on sixteen leaves, and the tentacles of all, as well as the blades of several, soon became greatly inflected. The periods were recorded in only three cases namely, with leaves on which unusually small drops had bee~ placed. Their tentacles were somewhat inflected in 45 m.; and after 7 hrs. 45 m. the blades of two were so much curved inwards that they formed little cups enclosing the drops. These leaves re-expanded on the third day. On another occasion the blade of a leaf was much inflected in 5 hrs. after a drop of milk had been placed on it. lJuman Un'ne.-Drops were placed on twelve leaves, and the tentacles of all, with a single exception, became greatly inflected. Owing, I presume, to differences in the chemical nature of the urine on different occasions, the time required for the movements of the tentacles varied much, but was always effected in under 24 hrs. In two instances I recorded that all the exterior tentacles were completely inflected in 17 hrs., but not the blade of the leaf. In another case the edges of a leaf, after 2fi hrs. 30 m., became so strongly inflected that it waH converted into a cup. The power of urine does not lie in the urea, which, as we shall hereafter see, is inoperative. .Albumen (fresh from a hen's egg), placed on seven leaves, caused the tentacles of six of them to be well inflected. In one case the edge of the leaf itself became much curled in after 20 hrs. The one leaf which was unaffected remained so for 26 hrs., and was then treated with a drop of milk, and this caused the tentacles to bend inwards in 12 hrs. Cold Filtered Infusion of Raw Meat.-This was tried only on a single leaf, which had most of its outer tentacles and the blade inflected in 19 hrs. During subsequent years, I repeatedly used this infusion to test leaves which had been experimented |