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Show 150 DROSERA ROTUNDIFOLIA. . CHAP. VII. Having made some preliminary trials as a guide, five leaves were placed in the same little vessel in thirty minims of a solu. tion of ?ne part of the ni~ra~e to 7875 of water (1 gr. to 18 oz.); and this amount of :flu1d JUSt sufficed to cover them. After 2 hrs. 10 m. three of the leaves were considerably inflected, and the other two moderately. The glands of all became of so dark a red as almost to deserve to be called black. After 8 hrs. four of the leaves had all their tentacles more or less inflected; whilst the fifth, which I then perceived to be an old leaf, had only thirty tentacles inflected. Next morning, after 23 hrs. 40 m., all the leaves were in the same state, excepting that the old leaf had a few more tentacles inflected. Five leaves which had been placed at the same time in water were observed at the same intervals of time; after 2 hrs. 10m. two of them had four, one had seven, one had ten, of the long-headed marginal tentacles, and the fifth had four round·headed tentacles, inflected. After 8 hrs. there was no change in these leaves, and after 24 hrs. all the ~arginal tentacles had re-expanded; but in one leaf, a dozen, and In a second leaf, half a dozen, submarginal tentacles had become inflected. As the glands of the five leaves in the solution were simultaneously darkened, no doubt they had aU absorbed a nearly equal amount of the salt: and as 2 ~ 8 of a grain was given to the five leaves together, each got 1 -fi0 of a grain ('045 mg.). I did not count the tentacles on these leave8, which were moderately fine ones, but as the average number on thii·ty-one leaves was 192, it would be safe to assume that each bore on an average at least 160. If so, each of the darkened glands could have rec~ived only 230\,00 of a grain of the nitrate; and this caused the inflection of a great majority of the tentacles. This plan of immersing several leaves in the same vessel is a bad one, as it is impossible to feel sure that the more vigorous leaves do not rob the weaker ones of their share of the salt. The glands, moreover, must often touch one another or ~he sides of the vessel, and movement may have been thus exCited; but the corresponding leaves in water which were little inflected, though rather more so than com~only occurs were exposed in an almost equal degree to these same source~ ?f err?r· I will, therefore, give only one other experiment made In this .manner, though many were tried and all confirmed ~he foregoi~~ and following results. Four leaves were placed In forty mi.nims of a solution of one part to 10,500 of water; and assummg that they absorbed equally, each leaf received Tl5 2 of a grain (·0562 mg.). After 1 hr. 20 m. many of the tentacles on all four leaves were somewhat inflected. After CHAP. VII . NITRATE OF AMMONIA. 151 5 hrs. 30 m. two leaves had all their tentacles inflected· a third leaf all except the extreme marginals, which seemed 'old and torpid; and the fourth a large number. After ~1 hrs. every single tentacle, on all four leaves, was closely inflected. Of the four leaves placed at the same time in water, one had, after 5 hrs. 45 m., five marginal tentacles inflected; a second ten; a third, nine marginals and submarginals; and the fourth ' twelve, chiefly submarginals, inflected. After 21 hrs. all thes~ marginal tentacles re-expanded, but a few of the ~ubmarginals on two of the leaves remained slightly curved inwards. The contrast was wonderfully great between these four leaves in water and those in the solution, the latter having every one of their tentacles closely inflected. Making the moderate assumption that each of these leaves bore 160 tentacles, each gland co~ld have. absorbed only 1 8 4 1 3 2 0 of a grain ('000351 mg.). This experiment was repeated on three leaves with the same relative amount of the solution; and after 6 hrs. 15 m. all the tentacles except nine, on all three leaves taken together were closely inflected. In this case the tentacles on each leaf were counted, and gave an average of 162 per leaf. The follo~ing experiments were tried during the summer of 1873, by placing the leaves, each in a separate watch-glass and pouring over it thirty minims (1·775 ml.) of the solution; other leaves being treated in exactly the same manner with the doubly distilled water used in making the solutions. The trials above given were made several years before, and when I read over my notes, I could not believe in the results ,· so I resolved to begin again with moderately strong solutions. Six leaves were first immersed, each in thirty minims of a solution of one part of the nitrate to H750 of water (1 gr. to 20 oz.), so that each received 3 ~o of a grain ('2025 mg.). Before 30 m. had elapsed, four of these leaves were immensely, and two of them moderately, inflected. The glands were rendered . of a dark 1·ed. The four corresponding leaves in water were not at all affected until 6 hrs. had elapsed, and then only the short tentacles on the borders of the disc ; and their inflection, as previously explained, is never 'of any significance. Four leaves were immersed, each in thirty minims of a solution. of one part to 17,500 of water (1 gr. to 40 oz.), so that each received 6 l 0 of a grain ('101 mg.); and in less than 45 m. three of them had., all their tentacles, except from four to ten, inflected; the blade of one being inflected after 6 hrs., and the blade of a second after 21 hrs. The four·th leaf was not at all affected. The glands of none were darkened. Of the corresponding leaves |