When a revolving shoot consists of several internodes, the lower ones
bend together at the same rate, but one or two of the terminal ones
bend at a slower rate; hence, though at times all the internodes are
in the same direction, at other times the shoot is rendered slightly
serpentine. The rate of revolution of the whole shoot, if judged by
the movement of the extreme tip, is thus at times accelerated or
retarded. One other point must be noticed. Authors have observed
that the end of the shoot in many twining plants is completely
hooked; this is very general, for instance, with the Asclepiadaceae.
The hooked tip, in all the cases observed by me, viz, in Ceropegia,
Sphaerostemma, Clerodendron, Wistaria, Stephania, Akebia, and
Siphomeris, has exactly the same kind of movement as the other
internodes; for a line painted on the convex surface first becomes
lateral and then concave; but, owing to the youth of these terminal
internodes, the reversal of the hook is a slower process than that of
the revolving movement. {10} This strongly marked tendency in the
young, terminal and flexible internodes, to bend in a greater degree
or more abruptly than the other internodes, is of service to the
plant; for not only does the hook thus formed sometimes serve to
catch a support, but (and this seems to be much more important) it
causes the extremity of the shoot to embrace the support much more
closely than it could otherwise have done, and thus aids in
preventing the stem from being blown away during windy weather, as I
have many times observed. In Lonicera brachypoda the hook only
straightens itself periodically, and never becomes reversed. I will
not assert that the tips of all twining plants when hooked, either
reverse themselves or become periodically straight, in the manner
just described; for the hooked form may in some cases be permanent,
and be due to the manner of growth of the species, as with the tips