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Show 22 DROSERA ROTUNDIFOLIA. CrrAP. II. outer tentacles to bend inward~. B~t .this foll~ws much more surely and quickly, If the. obJect conta1ns nitroaenous matter which can be dissolved by the secre btI. on. On one occasion I obser.v ed the follow- · unusual circumstance. Small hits of raw meat Ing · h h b (which acts n1ore energetically t an any ot . r su - stance), of paper, dried moss, and of the quill of a pen were placed on several leaves, and th y were all embraced equally well in about 2 hrs. On other occasions the above-named substances, or more commonly particles of glass, coal-cinder ( tak n. fro In tho fire), stone, gold-leaf, dried grass,. cork,. blotting-paper, cotton-wool, and hair rolled up Into little balls, were used, and these substances, though they were sometimes well embraced, often caused no n1ovement whatever in the outer tentacles, or an extremely slight and slow moven1ent. Yet these same leaves w re prov d. to be in an active condition, as they were xcited to move by substances yielding soluble nitrogenous m~tter,. such as bits of raw or roast meat, the yolk or "\Yhite of boiled eggs, fragments of insects of all orders, spiders, &c. I will give only two instances. Minute flies were placed on the discs of several leav s, and on others balls of paper, bits of moss and quill of about th same size as the flies, and the latter were well n1braced in a few hours; whereas after 25 hrs. only a very few tentacles were inflected ov r the other objects. The bits of paper, moss, and quill were then removed from these leaves, and bits of raw meat placed on them; and now all the tentacles were ·soon energetically inflected. Again, particles of coal-cinder (weighing rather more than the flies used in the last experiment) were placed on the centres of three leaves: aft r an interval of 19 hrs. one of the particles was tolerably well embraced; CHAP. II. INFLECTION INDIRECTLY CAUSED. 23 a second by a very few tentacles; and a third by none. I then removed the particles from the two latter leaves, and put on them recently killed flies. These were fairly well embraced in 7! hrs. and thoroughly after 20!- hrs. ; the tentacles re1naining inflected for many subsequent days. On the other hand, the one leaf which had in the course of 19 hrs. embraced the bit of cinder moderately well, and to which no fly was given, after an additional 33 hrs. (i.e. in 52 hrs. from the time when the cinder was put on) was comp~etely re-expanded and ready to act again. From these and numerous other experiments not worth giving, it is certain that inorganic substances, or such organic substances as are not attacked by the secretion, act much less quickly and efficiently than organic substances yielding soluble matter which is absorbed. Moreover, I have met with very few exceptions to the rule, and these exceptions apparently depended on the leaf having been too recently in action, that the tentacles remain clasped for a much longer time over organic bodies of the nature just specified than over those which are not acted on by the secretion, or over inorganic objects.* * Owing to the extraordinary belief held bv 1\'I. Ziegler (' Comptes rend us,' May 1872, p. 122), that albunlinous substances, if held for· a moment between the fingers, acquire the property of making the tentacles of Drosera contract, whereas, if not thus held, they have no such power, I tried some experiments with great care, but the results did not confirm this belief. Red-hot cinders were taken out of the fire, and bits of glass, cotton-thread, blotting paper and thin slices of cork were immersed in boiling water; and particles were then placed (every instrument with which they "\.Yere touched having been previously immersed in boiling water) on the glands of several leaves, and they acted in exactly the same manner as other particles, which had been purposely handled for some time. Bits of a boiled egg, cut with a knife which had been washed in boiling water, also acted like any other animal substance. I breathed on some leaves for above a minute, and repeated the act two or three times, with my mouth close to |