a a E ON 
Cair. XI] GENERAL SUMMARY. 225 
then the glands, being thus excited, send back some other 
influence (not dependent on increased secretion, nor on the 
inflection of the tentacles), causing the protoplasm to 
aggregato in cell beneath cell. This may be called a reflex 
action, though probably very different from that proceeding 
from the nerve-ganglion of an animal; and it is the only 
known case of reflex action in the vegetable kingdom. : 
About the mechanism of the movements and the nature of 
the motor impulse we know very little. During the act of 
inflection fluid certainly travels from one part to another of 
the tentacles. But the hypothesis which agrees best with 
the observed facts is that the motor impulse is allied in nature 
to the aggregating process; and that this causes the mole- 
cules of the cell-walls to approach each other, in the same 
manner as do the molecules of the protoplasm within the 
cells; so that the cell-walls contract, But some strong 
objections may be urged against this view. The re-expansion 
of the tentacles is largely due to the elasticity of their outer 
cells, which comes into play as soon as those on the inner 
side cease contracting with prepotent force; but we have 
reason to suspect that fluid is continually and slowly attracted 
into the outer cells during the act of re-expansion, thus 
increasing their tension.* 
I have now given a brief recapitulation of the chief points 
observed by me, with respect to the structure, movements, 
constitution, and habits of Drosera rotundifolia ; and we see 
how little has been made out in comparison with what 
remains unexplained and unknown. 
* [Increase of fluid iv the external (convex) cells would tend to prevent 
re-expansion, not to facilitate it—F. D.] 
