One of my plants bore two shoots near together, and the tendrils were
repeatedly drawn across one another, but it is a singular fact that
they did not once catch each other. It would appear as if they had
become habituated to contact of this kind, for the pressure thus
caused must have been much greater than that caused by a loop of soft
thread weighing only the one-sixteenth of a grain. I have, however,
seen several tendrils of Bryonia dioica interlocked, but they
subsequently released one another. The tendrils of the Echinocystis
are also habituated to drops of water or to rain; for artificial rain
made by violently flirting a wet brush over them produced not the
least effect.
The revolving movement of a tendril is not stopped by the curving of
its extremity after it has been touched. When one of the lateral
branches has firmly clasped an object, the middle branch continues to
revolve. When a stem is bent down and secured, so that the tendril
depends but is left free to move, its previous revolving movement is
nearly or quite stopped; but it soon begins to bend upwards, and as
soon as it has become horizontal the revolving movement recommences.
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