Twenty leaves were first carefully examined, and re-examined after
having been left immersed in distilled water for various periods, with
the following results. It is rare to find even a trace of aggregation
until 4 or 5 and generally not until several more hours have elapsed.
When however a leaf becomes quickly inflected in water, as sometimes
happens, especially during very warm weather, aggregation may occur in
little over 1 hr. In all cases leaves left in water for more than 24
hrs. have their glands blackened, which shows that their contents are
aggregated; and in the specimens which were carefully examined, there
was fairly well-marked aggregation in the upper cells of the pedicels.
These trials were made with cut off-leaves, and it occurred to me that
this circumstance might influence the result, as the footstalks would
not perhaps absorb water quickly enough to supply the glands as they
continued to secrete. But this view was proved erroneous, for a plant
with uninjured roots, bearing four leaves, was submerged in distilled
water for 47 hrs., and the glands were blackened, though the tentacles
were very little inflected. In one of these leaves there was only a
slight degree of aggregation in the tentacles; in the second rather
more, the purple contents of the cells being a little separated from
the walls; in the third and fourth, which were pale leaves, the
aggregation in the upper parts of the pedicels was well marked. In
these leaves the little masses of protoplasm, many of which were oval,
slowly changed their forms and positions; so that a submergence for 47
hrs. had not killed the protoplasm. In a previous trial with a
submerged plant, the tentacles were not in the least inflected. [page
53]
Heat induces aggregation. A leaf, with the cells of the tentacles
containing only homogeneous fluid, was waved about for 1 m. in water at
130 Fahr. (54 .4 Cent.) and was then examined under the microscope as
quickly as possible, that is in 2 m. or 3 m.; and by this time the
contents of the cells had undergone some degree of aggregation. A
second leaf was waved for 2 m. in water at 125 (51 .6 Cent.) and
quickly examined as before; the tentacles were well inflected; the
purple fluid in all the cells had shrunk a little from the walls, and
contained many oval and elongated masses of protoplasm, with a few
minute spheres. A third leaf was left in water at 125 , until it
cooled, and when examined after 1 hr. 45 m., the inflected tentacles
showed some aggregation, which became after 3 hrs. more strongly
marked, but did not subsequently increase. Lastly, a leaf was waved for
47