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Show 68 DROSERA ROTUNDIFOLIA. 0IIAP. IV. wl~en the leaves are subsequently placed in a solution of carbonate of ammonia. But the most remarkable change is that the O'lands become opaque and uniformly white; and this may be attributed to the coagulation of their albuminous contenf s. My first and preliminary experiment consisted in putting seven leaves in the same vessel of water, and warming it slowly up to the temperature of 110° Fahr. ( 43°·3 Cent.); a leaf being taken out as soon as the temperature rose to 80° (26°·6 Cont.), another at 85°, another at 90°, and so on. Each leaf, when taken out, was placed in water at thE\ temperature of my room, and the tentacles of all soon became slightly, though irTogularly, inflected. They were now removed from the cold water and kept in damp air, with bits of meat placed on their di.-cs. The leaf which had been exposed to the temperature of 110° became in 15 m. greatly inflected; and in 2 hrs. every single tentacle closely embraced the meat. So it was, but after rather longer intervals, with the six other leaves. It appears, therefore, that the warm bath had increased their sensitiveness when excited by meat. I next observed the degree of inflection which leaves under went within stated periods, whilst still immersed in warm water, kept as nearly as possible at the same temperature ; but I will here and elsewhere give only a few of the many trials made. A leaf was left for 10 m. in water at 100° (37°·7 Cent.), but no inflection occurred. A second leaf, however, treated in the same manner, had a few of its exterior tentacles very slightly inflected in 6 m., and several irregularly but not closely inflected in 10 m. A third leaf, kept in water at 105° to 106° (40°.5 to 41°'1 Cent.), was very moderately inflected in 6 m. A fourth leaf, in water at 110° (43°·3 Cent.), was somewhat inflected in 4 m., and considerably so in from 6 m. to 7 rn. Three leaves were placed in water which was heated rather quickly, and by the time the temperature rose to 115°- 116° (46°·1 to 46°·06 Cent.), all three were inflected. I then removed the lamp, and in a few minutes every single tentacle , was closely mflected. The protoplasm within the cells was not killed, for it was seen to be in distinct movement· and tho leave~, havi11g be~n left in ~old water for 20 hrs., re~expanded. Another leaf was Immersed m water at 100° (37°·7 Cent.) which was raised to 120° .C48°·8 Cent.); and all the tentacles,' except the extreme margmal ones, soon became closely inflecteO.. The leaf was now placed in cold water, and in 7 hrs. 30 m. it ~1ad part~y, a?d in 10 hrs. fully, re-expanded. On the followmg mornmg It was immersed in a weak solution of carbonate of CHAP. IV. THE EFFECTS OF HEAT. 69 ammonia, and the glands quickly became black, with strongly marked aggr~gation in the tentacles, showing that the protoplasm was ahve, and that the glands had not lost their power of absorption. Another leaf was placed in water at 110° (43°·3 Cent.) which was raised to 120° (48°·8 Cent.); and every tentacle, excepting one, was quickly a.nd closely inflected. This leaf was now immersed in a few drops of a strong solution of carbonate of ammonia (one part to 109 of water); in 10m. all the glands beca1ne intensely black, and in 2 hrs. the protoplasm in the cells of the pedicels was well aggregated. Another leaf was suddenly plunged, and as usual waved about, in water at 120°, and the tentacles became inflected in from 2m. to 3m., but only so as to stand at right angles to the disc. The leaf was now placed in the same solution (viz. one part of carbonate of ammonia to 109 of water, or 4 grs. to 1 oz., which I will for the future designate as the strong solution), and when I looked at it again after the interval of an hour, the glands were blackened, and there was well-marked aggregation. After an additional interval of 4 hrs. the tentacles had become much more inflected. It deserves notice that a solution as strong as this never causes inflection in ordinary cases. Lastly a leaf was suddenly placed in water at 125° (51°·6 Cent.), and was left in it until the water cooled; the tentacles were rendered of a bright red and soon became inflected. The contents of the cells underwent some degree of aggregation, which in the course of three hours increased; but the masses of protoplasm did not become spherical, as almost always occurs with leaves immersed in a solution of carbonate of ammonia. We learn from these cases that a temperature of from 120° to 125° ( 48°·8 to 51 °'6 Cent.) excites the tentacles into quick movement, but does not kill the leaves, as shown either by their subsequent re-expansion or by the aggregation of the protoplasm. vV e shall now see that a temperature of 130° (54°·4 Cent.) is too high to cause immediate inflection, yet does not kill the leaves. . Experiment 1.-A leaf was plunged, and as in all cases waved about for a few minutes, in water at 130° (54°'4 Cent.), but there was no trace of inflection; it was then placed in cold water, and after an interval of 15 m. very slow movement was |