a filament, by the aid of a needle moved with extreme slowness, bits of
rather thick human hair, and these did not excite movement, although
they were more than ten times as long as those which caused the
tentacles of Drosera to bend; and although in this latter case they
were largely supported by the dense secretion. On the other hand, the
glands of Drosera may be struck with a needle or any hard object, once,
twice, or even thrice, with considerable force, and no movement ensues.
This singular difference in the nature of the sensitiveness of the
filaments of Dionaea and of [page 290] the glands of Drosera evidently
stands in relation to the habits of the two plants. If a minute insect
alights with its delicate feet on the glands of Drosera, it is caught
by the viscid secretion, and the slight, though prolonged pressure,
gives notice of the presence of prey, which is secured by the slow
bending of the tentacles. On the other hand, the sensitive filaments of
Dionaea are not viscid, and the capture of insects can be assured only
by their sensitiveness to a momentary touch, followed by the rapid
closure of the lobes.
As just stated, the filaments are not glandular, and do not secrete.
Nor have they the power of absorption, as may be inferred from drops of
a solution of carbonate of ammonia (one part to 146 of water), placed
on two filaments, not producing any effect on the contents of their
cells, nor causing the lobes to close, When, however, a small portion
of a leaf with an attached filament was cut off and immersed in the
same solution, the fluid within the basal cells became almost instantly
aggregated into purplish or colourless, irregularly shaped masses of
matter. The process of aggregation gradually travelled up the filaments
from cell to cell to their extremities, that is in a reverse course to
what occurs in the tentacles of Drosera when their glands have been
excited. Several other filaments were cut off close to their bases, and
left for 1 hr. 30 m. in a weaker solution of one part of the carbonate
to 218 of water, and this caused aggregation in all the cells,
commencing as before at the bases of the filaments.
Long immersion of the filaments in distilled water likewise causes
aggregation. Nor is it rare to find the contents of a few of the
terminal cells in a spontaneously aggregated condition. The aggregated
[page 291] masses undergo incessant slow changes of form, uniting and
again separating; and some of them apparently revolve round their own
axes. A current of colourless granular protoplasm could also be seen
256