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Show 31G DAR WIN IAN A. not last long; the particles of "aggregated protoplasm" redissolve, the process of redissolution traveling upward from the base of the tentacle to the gland iu a reverse direction to that of the aggregation. Whenever the action is more prolonged or intense, as when a bit of meat or crushed fly, or a fitting solution, is left upon· the gland, the aggregation proceeds further, so that the whole protoplasm of each cell condenses into one or two masses, or into a single mass which will often separate into two, which afterward reunite ; indeed, they incessantly change their forms and positions, being never at rest, although their movements are rather slow.- In appearance and movements they are very like amcebrn and the white cor-. puscles of the blood. Their motion, along with the streaming movement of rotation in the layer of white granular protoplasm that flows along the walls of the cell, under the high powers of the microscope " pre sents a wonderful scene of vital activity." This continues while the tentacle is inflected or the gland fed by animal matter, but vanishes by dissolution when the work is over and the- tentacle straightens. That absorption takes place, ana matter is conveyed from cell to cell, is well made out, especially by the experiments with carbonate of ammonia. Nevertheless, this aggregation is not dependent upon absorption, for it equally occurs from mechanical irritation of the gland, and always accompanies inflection, however caused, though it may take place without it. This is also apparent from the astonishingly minute quantity of certain substances which suffices to produce sensible inflection and aggregati :m_:_such, for instance, as the INSECTIVOROUS AND CLIMBING PLANTS. 317 2 o o o1o o o o or even the ~0 of a grain of phosphate or nitrate of ammonia ! By varied experiments it was found that the nitrate of ammonia was more powerful than the carbonate, and the phosphate more powerful than the nitrate, this result being intelligible from the difference in the amount of nitrogen in the first two salts, and from the presence of phosphorus in the third. There is nothing surprising in the absorption of such extremely dilute solutions by a gland. As our author remarks : ''All physiologists admit that .the roots of plants absorb the salts of ammonia brought to them by the rain ; and fourteen gallons of rain-water [i. e., early rainwater] contain a grain of ammonia;· therefore, only a little more than twice as much as in the weakest solution employed by me. The fact which appears truly wonderful is that the 2 0 0 0 1 0 0 0 0 of a grain of the phosphate of ammonia, including less than 3 0 0 0 \ 0 0 0 of efficient matter [if the water of crystallizfttion is deducted], when absorbed by a gland, should induce some change in it which leads to a motor impulse being transmitted down the whole length of the tentacle, causing its basal part to bend, often through an angle of .180°." But odoriferous particles which act upon the nerves of animals must be infinitely smaller, and by these a dog a quarter of a mile to the leeward of a deer perceives his presence by some change in the olfactory nerves transmitted through them to the brain. When Mr. Darwin obtained these results, fourteen years ago, he could claim for .Drosera a power and delicacy in the detection of minute quantities of a sub- |
