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Show 166 DROSERA ROTUNDIFOLIA. CHAP. vn. absorbed only TIJ"7-loooo of a grain, or ·00000328 mg.; and this excessively minute amount sufficed to cause all the tentacles bearing these glands to be greatly inflected. The blade was also inflected. Summary of the Results with Phosphate of Am1nonia.The glands of the disc, when excited by a half-minim drop ('0296 ml.), containing 38 1·:n r of a grain ('0169 mg.) of this salt, transmit a motor impulse to the exterior tentacles, causing them to bend inwards. A 1ninute drop, containing Ttioocr of a grain ('000423 n1g.), 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 a shorter time, in a solution so weak that each gland can absorb only the Tno1u 0 0 0 of a grain ('00000328 mg.), this is enough to excite the tentacle into moven1ent, so that it becomes closely inflected, as does sometimes the blade. In the general summary to this chapter a few remarks will be added, showing that the efficiency of such extremely minute doses is not ·so incredible as it must at first appear. Sulphate of .Ammonia.-The few trials made with this and the following five salts of ammonia were undertaken merely to ascertain whether they induced inflection. Half-minims of a solution of one part of the sulphate of ammonia to 437 of water were placed on the discs of seven leaves, so that each received 9 ~ 0 of a grain, or ·0675 mg. After 1 hr. the tentacles of five of them, as well as the blade of one, were strongly inflected. '.l'he leaves were not afterwards observed. Citrate of .Ammoniu.-Half-minims of a solution of one part to 437 of water were placed on the discs of six leaves. In · 1 hr. the short outer tentacles round the discs were a little inflected, with the glands on the discs blackened. After 3 hrs. 25 m. one leaf had its blade inflected but none of the exterior tentacles. All six leaves remained in' nearly the same state during the day, the submarginal tentacles, however, CHAP. VII. OTHER SALTS OF AMMONIA. 167 becoming more inflected. After 23 hrs. three of the leaves had their blades somewhat inflected; and the submarginal tentacles of all considerably inflected, but in none were the two, three, or four outer rows affected. I have rarely seen cases like this, except from the action of a decoction of grass. The glands on the discs of the above leaves, instead of being almost black, as after the first hour, were now after 23 hrs. very pale. I next tried on four leaves half-minims of a weaker solution, of one part to 131~ of water (1 gr. to 3 oz.); so that each received 2 l so of a grain ('0225 mg.). After 2 hrs. 18 m. the glands on the disc were very dark-coloured; after 24 hrs. two of the leaves were slightly affected; the other two not at all. Acetate of Ammorda.-·Half-minims of a solution of about one part to 109 of water were placed on the discs of two leaves, both of which were acted on in 5 hrs. 30 m., and after 23 hrs. had every single tentacle closely inflected. Oxalate of Ammonia.-Half-minims of a solution of one part to 218 of water were placed on two leaves, which, after 7 hrs., became moderately, and after 23 hrs. strongly, inflected. Two other leaves were tried with a weaker solution of one part to 437 of water; one was strongly inflected in 7 hrs.; the other not until 30 hrs. had elapsed. Turtrate of A.mnwnia.-Half-minims of a solution of one part to 437 of water were placed on the discs of five leaves. In 31 m. there was a trace of inflection in the exterior tentacles of some of the leaves, and this became more decided after 1 hr. with all the leaves; but the tentacles were never closely inflected. After 8 hrs. 30 m. they began to re-expand. Next morning, after 23 hrs., all were fully re-expanded, excepting one which was still slightly inflected. The shortness of the period of inflection in this and the following case is remarkable. Cltloride of Ammonium.- Half-minims of a solution of one part to 437 of water were placed on the discs of six leaves. A decided degree of inflection in the outer and submarginal tentacles was perceptible in 25 m.; and this increased during the next three or four hours, but never became strongly marked. After only 8 hrs. 30 m. the tentacles began to re-expand, and by the next morning, after 24 1ll's., were fully re-expanded on four of the leaves, but still slightly inflected on two. General Summary and Concluding Remarks on the Salts of Am1nonia.-W e have now seen that the nine |