256 DROSERA ROTUNDIFOLIA,. Cuap. X. 
the bending tentacle. But it does not follow from 
these observations that the cells on the convex side 
become filled with more fluid during the act of in- 
flection than they contained before; for fluid may all 
the time be passing into the disc or into the glands 
which then secrete freely. 
The bending of the tentacles, when leaves are im- 
mersed in a dense fluid, and their subsequent re- 
expansion in a less dense fluid, show that the passage 
of fluid from or into the cells can cause movements 
like the natural ones. But the inflection thus caused 
is often irregular; the exterior tentacles being some- 
times spirally curved. Other unnatural movements 
are likewise caused by the application of dense fluids, 
as in the case of drops of syrup placed on the backs 
of leaves and tentacles. Such movements may be 
compared with the contortions which many vegetable 
tissues undergo when subjected to exosmose. It is 
therefore doubtful whether they throw any light on 
the natural movements. 
If we admit that the outward passage of fluid is 
the cause of the bending of the tentacles, we must 
suppose that the cells, before the act of inflection, 
are in a high state of tension, and that they are 
elastic to an extraordinary degree; for otherwise their 
contraction could not cause the tentacles often to 
sweep through an angle of above 180°. Professor 
Cohn, in his interesting paper* on the movements 
of the stamens of certain Composite, states that these 
organs, when dead, are as elastic as threads of india- 
rubber, and are then only half as long as they were 
when alive. He believes that the living protoplasm 
* ‘Abhand. der Schles. Gesell. is given in the ‘ Annals and Mag. 
fiir vaterl. Cultur, 1861, Heft i. of Nat. Hist.’ 3rd series, 1868, 
An exocllent abstract of this paper vol. xi. pp. 188-197. 
