Cuar. IV.) THE EFFECTS OF HEAT. 6} 
then in the strong solution, the cells in the tentacles became of a 
muddy greenish brown, with the protoplasm not aggregated. Never- 
theless, 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 alterwards 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 ex- 
tremely 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 
sec 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 tempera- 
ture 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* 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, they generally, though not 
* ¢Traité de Bot.’ 1874, p. 1034. 
