We have seen that leaves immersed for some hours in dense solutions of
sugar, gum, and starch, have the contents of their cells greatly
aggregated, and are rendered more or less flaccid, with the tentacles
irregularly contorted. These leaves, after being left for four days in
distilled water, became less flaccid, with their tentacles partially
re-expanded, and the aggregated masses of protoplasm were partially
redissolved. A leaf with its tentacles closely clasped over a fly, and
with the contents of the cells strongly aggregated, was placed in a
little sherry wine; after 2 hrs. several of the tentacles had
re-expanded, and the others could by a mere touch be pushed back into
their properly expanded positions, and now all traces of aggregation
had disappeared, the cells being filled with perfectly homogeneous pink
fluid. The redissolution in these cases may, I presume, be attributed
to endosmose.]
_On the Proximate Causes of the Process of Aggregation._
As most of the stimulants which cause the inflection of the tentacles
likewise induce aggregation in the contents of their cells, this latter
process might be thought to be the direct result of inflection; but
this is not the case. If leaves are placed in rather strong solutions
of carbonate of ammonia, for instance of three or four, and even
sometimes of only two grains to the ounce of water (i.e. one part to
109, or 146, or [page 55] 218, of water), the tentacles are paralysed,
and do not become inflected, yet they soon exhibit strongly marked
aggregation. Moreover, the short central tentacles of a leaf which has
been immersed in a weak solution of any salt of ammonia, or in any
nitrogenous organic fluid, do not become in the least inflected;
nevertheless they exhibit all the phenomena of aggregation. On the
other hand, several acids cause strongly pronounced inflection, but no
aggregation.
It is an important fact that when an organic or inorganic object is
placed on the glands of the disc, and the exterior tentacles are thus
caused to bend inwards, not only is the secretion from the glands of
the latter increased in quantity and rendered acid, but the contents of
the cells of their pedicels become aggregated. The process always
commences in the glands, although these have not as yet touched any
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