or expand as soon as the contraction of the upper surface diminishes. A
leaf was cut off and suddenly plunged perpendicularly into boiling
water: I expected that the lobes would have closed, but instead of
doing so, they diverged a little. I then took another fine leaf, with
the lobes standing at an angle of nearly 80o to each other; and on
immersing it as before, the angle suddenly increased to 90o. A third
leaf was torpid from having recently re-expanded after having caught a
fly, so that repeated touches of the filaments caused not the least
movement; nevertheless, when similarly immersed, the lobes separated a
little. As these leaves were inserted perpendicularly into the boiling
water, both surfaces and the filaments [page 320] must have been
equally affected; and I can understand the divergence of the lobes only
by supposing that the cells on the lower side, owing to their state of
tension, acted mechanically and thus suddenly drew the lobes a little
apart, as soon as the cells on the upper surface were killed and lost
their contractile power. We have seen that boiling water in like manner
causes the tentacles of Drosera to curve backwards; and this is an
analogous movement to the divergence of the lobes of Dionaea.
In some concluding remarks in the fifteenth chapter on the Droseraceae,
the different kinds of irritability possessed by the several genera,
and the different manner in which they capture insects, will be
compared. [page 321]
CHAPTER XIV.
ALDROVANDA VESICULOSA.
Captures crustaceans Structure of the leaves in comparison with those
of Dionaea Absorption by the glands, by the quadrifid processes, and
points on the infolded margins Aldrovanda vesiculosa, var.
australis Captures prey Absorption of animal matter Aldrovanda
vesiculosa, var. verticillata Concluding remarks.
This plant may be called a miniature aquatic Dionaea. Stein discovered
in 1873 that the bilobed leaves, which are generally found closed in
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