Page:Insectivorous Plants, Darwin, 1899.djvu/89

 in some cases their blades, well inflected; but their powers were somewhat impaired, for the rate of movement was decidedly slower than when fresh leaves were treated with these same nitrogenous fluids. This impairment, as well as the insensibility of six of the leaves, may be attributed to injury from exosmose, caused by the density of the fluids placed on their discs. The results of a few other experiments with nitrogenous fluids may be here conveniently given. Decoctions of some vegetables known to be rich in nitrogen, were made, and these acted like animal fluids. Thus, a few green peas were 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 an incoagulable solution,” and this would mingle with boiling water. I may mention, in relation to the above and following experiments, that according to Schiff certain forms of albumen 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 1¼ hr. ; and by decanting the decoction after it had been allowed to rest, a pale dirty green fluid was obtained. The usual-sized 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 secretion 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 quantity 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 boiling point. Drops of this infusion were placed on four leaves. One of these, after 2.3 hrs., was much inflected; a second slightly; a third had only the submarginal tentacles inflected; and the fourth was not at all af-