I witnessed this repeatedly; and it occurred both
when the supporting internodes were free and when they were tied up;
but was perhaps most conspicuous in the latter case, or when the
whole shoot happened to be much inclined. The tendril forms a very
acute angle with the projecting extremity of the stem or shoot; and
the stiffening always occurred as the tendril approached, and had to
pass over the shoot in its circular course. If it had not possessed
and exercised this curious power, it would infallibly have struck
against the extremity of the shoot and been arrested. As soon as the
tendril with its three branches begins to stiffen itself in this
manner and to rise from an inclined into a vertical position, the
revolving motion becomes more rapid; and as soon as the tendril has
succeeded in passing over the extremity of the shoot or point of
difficulty, its motion, coinciding with that from its weight, often
causes it to fall into its previously inclined position so quickly,
that the apex could be seen travelling like the minute hand of a
gigantic clock.
The tendrils are thin, from 7 to 9 inches in length, with a pair of
short lateral branches rising not far from the base.
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