Concluding Remarks.--As the hair-like tentacles are extremely thin and have delicate walls, and as the leaves were waved about for some minutes close to the bulb of the thermometer, it seems scarcely possible that they should not have been raised very nearly to the temperature which the instrument indicated. From the eleven last observations we see that a temperature of 130o (54o.4 Cent.) never causes the immediate inflection of the tentacles, though a temperature from 120o to 125o (48o.8 to 51o.6 Cent.) quickly produces this effect. But the leaves are paralysed only for a time by a temperature of 130o, as afterwards, whether left in simple water or in a solution of carbonate of ammonia, they become inflected and their protoplasm undergoes aggregation. This great difference in the effects of a higher and lower temperature may be compared with that from immersion in strong and weak solutions of the salts of ammonia; for the former do not excite movement, whereas the latter act energetically. A temporary suspension of the [page 73] power of movement due to heat is called by Sachs* heat-rigidity; and this in the case of the sensitive-plant (Mimosa) is induced by its exposure for a few minutes to humid air, raised to 120o-122o Fahr., or 49o to 50o Cent. It deserves notice that the leaves of Drosera, after being immersed in water at 130o Fahr., are excited into movement by a solution of the carbonate so strong that it would paralyse ordinary leaves and cause no inflection.
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 immersed in boiling water; and this apparently is due to their passive power of elasticity. After exposure to a temperature of 150o 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 leaves 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 immersed in water raised to 156o (68o.8 Cent.), escaped being rendered porcellanous;* and the protoplasm in the cells close beneath these glands underwent some slight, though imperfect, degree of aggregation.