A recapitulation of the chief facts and discussions in this chapter
will be given at the close of the next chapter. [page 262]
CHAPTER XI.
RECAPITULATION OF THE CHIEF OBSERVATIONS ON DROSERA ROTUNDIFOLIA.
As summaries have been given to most of the chapters, it will be
sufficient here to recapitulate, as briefly as I can, the chief points.
In the first chapter a preliminary sketch was given of the structure of
the leaves, and of the manner in which they capture insects. This is
effected by drops of extremely viscid fluid surrounding the glands and
by the inward movement of the tentacles. As the plants gain most of
their nutriment by this means, their roots are very poorly developed;
and they often grow in places where hardly any other plant except
mosses can exist. The glands have the power of absorption, besides that
of secretion. They are extremely sensitive to various stimulants,
namely repeated touches, the pressure of minute particles, the
absorption of animal matter and of various fluids, heat, and galvanic
action. A tentacle with a bit of raw meat on the gland has been seen to
begin bending in 10 s., to be strongly incurved in 5 m., and to reach
the centre of the leaf in half an hour. The blade of the leaf often
becomes so much inflected that it forms a cup, enclosing any object
placed on it.
A gland, when excited, not only sends some influence down its own
tentacle, causing it to bend, but likewise to the surrounding
tentacles, which become incurved; so that the bending place can be
acted on by an impulse received from opposite directions, [page 263]
namely from the gland on the summit of the same tentacle, and from one
or more glands of the neighbouring tentacles. Tentacles, when
inflected, re-expand after a time, and during this process the glands
secrete less copiously, or become dry. As soon as they begin to secrete
again, the tentacles are ready to re-act; and this may be repeated at
least three, probably many more times.
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