the cells of the twisted portions was aggregated into distinct though excessively minute purple spheres. This case shows clearly that the protoplasm, after having been exposed to a high temperature for a few minutes, is capable of aggregation when afterwards subjected to the action of carbonate of ammonia, unless the heat has been sufficient to cause coagulation.
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 130° (54°.4 Cent.) never causes
the immediate inflection of the tentacles, though a temperature
from 120° to 125° (48°.8 to 51°.6 Cent.) quickly
produces this effect. But the leaves are paralysed only for a
time by a temperature of 130°, 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 power of movement
due to heat is called by Sachs[1] 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 120°—
122° Fahr., or 49° to 50° Cent. It deserves notice that the
leaves of Drosera, after being immersed in water at 130°
Fahr., are excited into movement by a solution of the carbonate
so strong that it would paralyze ordinary leaves and
cause no inflection.
The exposure of the leaves for a few minutes even to a temperature of 145° Fahr. (62°.7 Cent.) does not always kill them; as, when afterwards left in cold water, or in a strong solution of carbonate of ammonia, they generally, though not always, become inflected; and the protoplasm within their cells undergoes aggregation, though the spheres thus formed are extremely small, with many of the cells
partly filled with brownish muddy matter. In two instances,
- ↑ 'Traité de Bot.' 1874, p. 1034.
