266 DROSERA ROTUNDIFOLIA. Crap. XL 
one part of the leaf to another must be different 
from that which actually induces aggregation. The 
process does not depend on the glands secreting 
more copiously than they did before; and is inde- 
pendent of the inflection of the tentacles. It con- 
tinues as long as the tentacles remain inflected, and as 
soon as these are fully re-expanded, the little masses 
of protoplasm are all redissolved ; the cells becoming 
filled with homogeneous purple fluid, as they were 
before the leaf was excited. 
As the process of aggregation can be excited by a 
few touches, or by the pressure of insoluble particles, 
it is evidently independent of the absorption of any 
matter, and must be of a molecular nature. Even when 
caused by the absorption of the carbonate or other 
salt of ammonia, or an infusion of meat, the process 
seems to be of exactly the same nature. The proto- 
plasmic fluid must, therefore, be in a singularly un- 
stable condition, to be acted on by such slight and 
varied causes. Physiologists believe that when a 
nerve is touched, and it transmits an influence to other 
parts of the nervous system, a molecular change is 
induced in it, though not visible to us. Therefore it 
is a very interesting spectacle to watch the effects on 
the cells of a gland, of the pressure of a bit of hair, 
weighing only +3155 of a grain and largely supported 
by the dense secretion, for this excessively slight 
pressure soon causes a visible change in the proto- 
plasm, which change is transmitted down the whole 
length of the tentacle, giving it at last a mottled 
appearance, distinguishable even by the naked eye. 
In the fourth chapter it was shown that leaves 
placed for a short time in water at a temperature of 
110° Fahr. (48°3 Cent.) become somewhat inflected ; 
they are thus also rendered more sensitive to the action 
