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Show 74 DROSERA ROTUNDIFOLIA. UIIAI'.IV. pinkish colour, and many present a speckled appearance. This high temperature never causes true inflection; on the contrary, the tentacles commonly become reflexed, though to a less degree than when i1nmcrsed in boiling water; and this apparently is due to their passive power of elasticity. After exposure to a temperature of 150° Fahr., the protoplasm, if subsequently subjected to carbonate of ammonia, instead of undergoing aggregation, is converted into disintegrated or pulpy discoloured matter. In short, the leav s are generally killed by this degree of heat; but owing to differences of age or constitution, they vary somewhat in this respect. In one anomalous case, four out of the many glands on a leaf, which had been im1nersed in water raised to 156° (68°·8 Cent.), escaped being rendered porcellanous ; * and the protoplasm in the cells close · beneath these glands underw nt some slight, though imperfect, degree of aggregation. Finally, it is a remarkable fact that the leaves of Drosera rotundifolia, which flourishes on bleak upland moors throughout Great Britain, and exists (Hooker) within the Arctic Circle, should be able to withstand for even a short time immersion in water heated to a temperature of 145°.t It may be worth adding that immersion in cold *As the opacity and porcelainlike appearance of the glands is probably due to the coagulation of the albumen, I may add, on the authority of Dr. Burdon Sanderson, that albumen coagulates at about 155°, but, in presence of acids, the temperature of coagulation is lower. The leaves of Drosera contain an acid, and perhaps a difference in the amount contained may account for the slight differences in the results above recorded. t It appears that cold-blooded animals are, as might have been expected, far more sensitive to an increase of temperature than is Drosera. Thus, a::; I hear from Dr. Burdon Sanderson, a frog begins to be distressed in water at a temperature of only 85° Fahr. At 95° the muscles become rigid, and the animal dies in a stiffened condition. CHAI'. IV. THE EFFECTS OF HEAT. '75 water does not cause any inflection: I suddenly placed four leaves, taken from plants which had been kept for several days at a high temperature, generally about 75° Fahr. (23°·8 Cent.), in water at 45° (7°·2 Cent.), but they were hardly at all affected; not so much as some other leaves from the same plants, which were at the same time immersed in water at 75o; for these became in a slight degree inflected. |
