of the leaf, causing all the glands to secrete and allowing them to
absorb the diffused animal matter. The movement, excited by the
absorption of such matter, though slow, suffices for its final purpose,
whilst the movement excited by one of the sensitive filaments being
touched is rapid, and this is indis- [page 309] pensable for the
capturing of insects. These two movements, excited by two such widely
different means, are thus both well adapted, like all the other
functions of the plant, for the purposes which they subserve.
There is another wide difference in the action of leaves which enclose
objects, such as bits of wood, cork, balls of paper, or which have had
their filaments merely touched, and those which enclose organic bodies
yielding soluble nitrogenous matter. In the former case the leaves, as
we have seen, open in under 24 hrs. and are then ready, even before
being fully-expanded, to shut again. But if they have closed over
nitrogen-yielding bodies, they remain closely shut for many days; and
after re-expanding are torpid, and never act again, or only after a
considerable interval of time. In four instances, leaves after catching
insects never reopened, but began to wither, remaining closed in one
case for fifteen days over a fly; in a second, for twenty-four days,
though the fly was small; in a third for twenty-four days over a
woodlouse; and in a fourth, for thirty-five days over a large Tipula.
In two other cases leaves remained closed for at least nine days over
flies, and for how many more I do not know. It should, however, be
added that in two instances in which very small insects had been
naturally caught the leaf opened as quickly as if nothing had been
caught; and I suppose that this was due to such small insects not
having been crushed or not having excreted any animal matter, so that
the glands were not excited. Small angular bits of albumen and gelatine
were placed at both ends of three leaves, two of which remained closed
for thirteen and the other for twelve days. Two other leaves remained
closed over bits of [page 310] meat for eleven days, a third leaf for
eight days, and a fourth (but this had been cracked and injured) for
only six days. Bits of cheese, or casein, were placed at one end and
albumen at the other end of three leaves; and the ends with the former
opened after six, eight, and nine days, whilst the opposite ends opened
a little later. None of the above bits of meat, albumen, &c., exceeded
a cube of 1/10 of an inch (2.54 mm.) in size, and were sometimes
smaller; yet these small portions sufficed to keep the leaves closed
for many days. Dr. Canby informs me that leaves remain shut for a
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