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Show 152 DROSERA ROTUNDIFOLIA. CHAP. VII. in water, only one bad any of its exterio~ tentacles, ~amely five, inflected· after 6 hrs. in one case, and after 21 hrs. In two other cases, tb~ short tentacles on the borders of the disc formed a ring, in the usual manner. . . . . . . Four leaves wore immersed, each In thirty minims of a solutwn of one part to 43,750 of water (1 gr. to 100 oz.), so that each l~af O'Ot __ 1_ of a grain ('0405 mg.). Of these, one was much mflect~ d0in 8 m., and after 2 brs. 7 m. had all the tentacles, except thirteen, inflected. Th~ second leaf, after 10m., had all except three inflected. The thud and fourt~ wore har~ly at all affected scarcely more than the corresponding leaves In water. Of the iattcr, only one was affected, this having two tentacles inflected with those on the outer parts of the disc formin g a rinO' in the usual manner. In the leaf which had all its tentacles except three inflected in 10m., each gland (assuming that the leaf bore 160 tentacles) could have absorbed only 251 1 2 00 of a grain, or ·000258 mg. Four leaves were separately immersed as before in a solution of one part to 131,250 of water (1 gr. to 300 oz.), so that each recel.ved __ 1 _ _ of a grain or ·0135 mg. After 50 m. one leaf had 4800 ' ' all its tentacles except sixteen, and after 8 hrs. 20 m. all but fourteen, inflected. The second leaf, after 40 m., had all but twenty inflected; and after 8 hrs. 10 m. began to re-expand. The third, in 3 hrs. had about half its tentacles inflected, which began to re-expand after 8 hrs. 15 m. 'I1he fourth leaf, after 3 hrs. 7 m., had only twenty-nine tentacles more or less inflected. Thus three out of the four leaves were strongly acted on. It is clear that very sensitive leaves had been accidentally selected. The day moreover was hot. The four corresponding leaves in water were likewise acted on rather more than is usual; for after 3 brs. one bad nine tentacles, another four, and another two, and the fourth none, inflected. With Tcspcct to the leaf of which all the tentacles, except sixteen, were inflected after 50 m., each gland (assuming that the leaf bore 160 tentacles) could have absorbed only ~00 of a grain ("0000937 mg.), and this appeal's to be about the least quantity of the nitrate which suffices to induce the intlection of a single tentacle. As negative Tesults are important in confirming the foregoing positive ones, eight leaves were immersed as before, each in thirty minims of a solution of one part to 175,000 of water (1 gr. to 400 oz.), so that each received only "ff4?00 of a grain ('0101 mg.). This minute quantity produced a slight effect on only four of the eight leaves. One had fifty-six tentacles inflected after 2 hrs. 13 m.; a second, twenty-six inflected, or sub-inflected, after CHA~. VII. PHOSPHATE OF AMMONIA. 153 38 m.; a third, eighteen inflected, after 1 hr.; and a fourth ten inflected, after 35 m. The four other leaves were not i~ the least affected. Of the eight corresponding leaves in water, one had, after 2 hrs. 10 m., nine tentacles, and four others from one to four long-headed tentacles, inflected; the remaining three being unaffected. Hence, the 7rioo of a grain given to a sensitive leaf during warm weather perhaps produces a slight effect; blft we must bear in mind that occasionally water causes as great an amount of inflection as occurred in this last experiment. Summary of the Results with Nitrate of Ammonia.The glands of the disc, when excited by a half-minim drop ('0296 ml.), containing 24 1 00 of a grain of the nitrate ('027 mg.), transmit a motor impulse to the exterior tentacles, causing them to bend inwards. A minute drop, containing 2 ll ~ 00 of a grain ('00225 mg.), if held for a few seconds in contact with a gland, causes the tentacle bearing this gland to be inflected If a leaf is left immersed for a few hours, and sometimes for only a few minutes, in a solution of such strength that each gland can absorb only the 09~00 of a grain ('0000937 mg.), this small amount is enough to excite each tentacle into movement, and it becomes closely inflected. PHOSPHATE OF AMMONIA. This salt is more powerful than the nitrate, even in a greater degree than the nitrate is more powerful than the carbonate. This is shown by weaker solutions of the phosphate acting when dropped on the discs, or applied to the glands of the exterior tentacles, or when leaves are immersed. The difference in the power of these three salts, as tried in three different ways, supports the results presently to be |
