moderately rigid and elastic; if bent by a needle, the upper end yields
more easily than the basal and thicker part, which alone is capable of
becoming inflected. The rigidity of this basal part seems due to the
tension of the outer surface balancing a state of active and persistent
contraction of the cells of the inner surface. I believe that this is
the case, because, when a leaf is dipped into boiling water, the
tentacles suddenly become reflexed, and this apparently indicates that
the tension of the outer surface is mechanical, whilst that of the
inner surface is vital, and is instantly destroyed by the boiling
water. We can thus also understand why the tentacles as they grow old
and feeble slowly become much reflexed. If a leaf with its tentacles
closely inflected is dipped into boiling water, these rise up a little,
but by no means fully re-expand. This may be owing to the heat quickly
destroying the tension and elasticity of the cells of the convex
surface; but I can hardly believe that their tension, at any one time,
would suffice to carry back the tentacles to their original position,
often through an angle of above 180o. It is more probable that fluid,
which we know travels along the tentacles during the act of inflection,
is slowly re-attracted into the cells of the convex surface, their
tension being thus gradually and continually increased.
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
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