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Show 270 DROSERA ROTUNDIFOLIA. .CHAP. XI. of the seedlings. It also absorbs 1natter from pollen, and from fragments of leaves. ~rhe seventh chapter was devoted to the action of the salts of ammonia. These all cause the tentacles, and often the blade of the leaf, to be inflected, and the protoplasm to be aggregated. They act with very different power; the citrate being the least powerful, and the phosphate, owing, no doubt, to the presence of phosphorus and nitrogen, by far the 1nost powerful. But the relative efficiency of only three salts of ammonia was carefully detennined, namely the carbonate, nitrate, and phosphate. The experiments were made by placing half-minims ('0296 ml.) of solutions of different strengths on the discs of the lea ves,-by applying a minute drop (about the ,_/0 of a minim, or ·00296 ml.) for a few seconds to three or four glands,and by the immersion of whole leaves in a n1easured quantity. In relation to these experin1ents it was necessary first to ascertain the effects of distilled water, and it was found, as described in detail, that the more sensitive leaves are affected by it, but only in a slight degree. A solution of the carbonat~ is absorbed by the roots and induces aggregation in their cells, but does not affect the leaves. The vapour is absorbed by the glands, and causes inflection as well as aggregation. A drop of a solution containing 1rfr-o of a grain ('0675 mg.) is the least quantity which, when placed on the glands of the disc, excites the exterior tentacles to bend inwards. But a minute· drop, containing T 4 {-00 of a grain ('00445 mg.), if applied for a few seconds to the secretion surrounding a gland, causes the inflection of the same tentacle. When a highly sensitive leaf is immersed in a solution and there is mple time for absorption, the - -. 1- ' of a grain ':t (j tl tl 0 0 CHAP. XI. GENERAL SUMMARY. 271 (·00024 mg.) is sufficient to excite a single tentacle into movement. The nitrate of ammonia induces aggregation of the protoplasm much less quickly than the carbonate, but is more potent in causing inflection. A drop containing 2 4 \ro· of a grain ( ·027 mg.) placed on the disc acts powerfully on all the exterior tentacles, which have not themselves received any of the solution ; whereas a drop with 28\r-o of a grain caused only a few of these tentacles to bend, but affected rather more plainly the blade. A minute drop applied as before, and containing ~ tl! 0 0 of a grain (·0025 mg.), caused the tentacle bearing this gland to bend. . By the immersion of whole leaves, it was proved that the absorption by a single gland of ()9~ of a grain ('0000937 mg.) was sufficient to set the same tentacle into movement. The phosphate of ammonia is much more powerful than the nitrate. A drop containing ti40 of a grain (·0169 mg.) placed on the disc of a sensitive leaf causes most of the exterior tentacles to be inflected, as well as the blade of the leaf. A minute drop containing TTJ-iooo of a grain ('000423 mg.), applied for a few seconds to a gland, acts, as shown by the moveInent of the tentacle. When a leaf is immersed in thirty minims (1·7748 ml.) of a solution of one part by weight of the salt to 21,875,000 of water, the absorption by a gland of only the 1 >> 7 ()1 0 0 o 0 of a grain ('00000328 mg.), that is, a little less than the onetwenty- Inillionth of a grain, is sufficient to cause the tentacle bearing this gland to bend to the centre of the leaf. In this experiment, owing to the presence of the water of crystallisation, less than the one-thirtymillionth of a· grain of the efficient elements could have been absorbed. There is nothing reinarkable in such minute quantities being absorbed by the glands, |
