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Show 82 DROSERA ROTUNDIFOLIA. CIIAP. v. nitrogenous 1natter by the glands of the tentacles on the disc. Some of the leaves which were not affected by tho 11on-nitroCYenous fluids were, as above stated, immediately afterwards tested with ~its of ll_l~at, and wo:c thus proved to be in an active condition. But In addition to these trials, twenty-three of the leave , with drops of gum, syrup, or starch, st~ll lyino- on their discs, which had produced no effect In the course of between 24 hrs. and 48 hrs., were then tested with drops of milk, urine, or albumen. Of ~he tw nty-three leaves thus treated, seventeen had then tentacles, and in some cases their blades, well inflected; but their powers were somewhat impaired, for the rate of moveJnent was decidedly slower than when fresh lea:res were treated with these same nitrogenous fluids. rrLis impairment, as well as the insensibility of six of the leaves, may be attributed to injury fro1n exosn1ose, caused by the density of the fluids placed on their discs. The results of a few other experiments with nitrogenous fluiuH may be here conveniently given. Decoctions of some vegetables, known to be rich in nitrogen, were made, and tho ·e acted like animal fluids. Thus, a few gre"n peas wore boiled for some time in distilled water, and the moderately thick decoction thus made was allowed to settle. Drops of the superincumbent fluid were placed on four leaves, and when these were looked at after 16 hrs., the tentacles and blades of all were found strongly inflected. I infer from a remark by Gerhardt* that legumin is present in peas "in combination with an alkali, forming rin incoagulable solution," and this would mingle with boiling water. I may mention, in relation to tho above and following experiments, that according to Schifft certain forms of albumen * 'Vatts' 'Diet. of Chemistry,' vnl. iii. p. 568. t ' Lec;ons sur la Phys. de la Digestion,' tom. i. p. 379; tom. ii. pp. 154, 166, on legumin. / "' CHAP. v. EFFECTS OF ORGANIC FLUIDS. 83 exist which are not coagulated by boiling water, but are converted into soluble peptones. On three occasions chopped cabbage-leaves* were boiled in distilled water for 1 hr. or for 1 ~ hr.; and by decanting the decoction after it had been allowed to rest, a pale dirty green fluid was obtained. The usual-siz::ed drops were placed on thirteen leaves. Their tentacles and blades were inflected after 4 hrs. to a quite extraordinary degree. Next day the protoplasm within the cells of the tentacles was found aggregated in the most strongly marked manner. I also touched the viscid secre- . tion round the glands of several tentacles with minute drops of the decoction on the head of a small pin, and they became well inflected in a few minutes. The fluid proving so powerful, one part was diluted with three of water, and drops were placed on the discs of five leaves; and these next morning were so much acted on that their blades were completely doubled over. We thus see that a decoction of cabbage-leaves is nearly or quite as potent as an infusion of raw meat. About the same quct,ntity of chopped cabbage-leaves and of distilled water, as in the last experiment, were kept in a vessel for 20 hrs. in a hot closet, but not heated to near the boilingpoint. Drops of this infusion were placed on four leaves. One of these, after 23 hrs., was much inflected; a second slightly; a third had only the submarginal tentacles inflected; and the fourth was not at all affected. The power of this infusion is therefore very much less than that of the decoction; and it is clear that the immersion of cabbage-leaves for an hour in water at the boiling temperature is much more efficient in extracting matter which excites Drosera than immersion during many hours in warm water. Perhaps the contents of the cells are protected (as Schiff remarks with respect to legumin) by the walls being formed of cellulose, and that untH these are ruptured by boiling-water, but little of the contained albumjnous matter is dissolved. We know from the strong odour of cooked cabbage-leaves that boiling water produces some chemical change in them, and that they are thus rendered far more digestible and nutritious to man. It is therefore an interesting * rrhe leaves of young plants, before the heart is formed, such as were used by me, contain 2 ·1 per cent. of albuminous matter, and the outer leaves of mature plants 1·6 per cent. Watts'' Diet. of Chemistry,' vol. i. p. 653. G 2 |