on the disc being still pinkish, those near the margin quite white. The
leaf being placed as usual first in cold water and then in the strong
solution, the cells in the tentacles became of a muddy greenish brown,
with the protoplasm not aggregated. Nevertheless, four of the glands
escaped being rendered like porcelain, and the pedicels of these glands
were spirally curled, like a French horn, towards their upper ends; but
this can by no means be considered as a case of true inflection. The
protoplasm within 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 [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 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 paralyse 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,
64