In speaking of plants which climb by the aid
of their branches, more or less modified, he states that the
following stages of development can be traced: (1.) Plants
supporting themselves simply by their branches stretched out at right
angles--for example, Chiococca. (2.) Plants clasping a support with
their unmodified branches, as with Securidaca. (3.) Plants climbing
by the extremities of their branches which appear like tendrils, as
is the case according to Endlicher with Helinus. (4.) Plants with
their branches much modified and temporarily converted into tendrils,
but which may be again transformed into branches, as with certain
Papilionaceous plants. (5.) Plants with their branches forming true
tendrils, and used exclusively for climbing--as with Strychnos and
Caulotretus. Even the unmodified branches become much thickened when
they wind round a support. I may add that Mr. Thwaites sent me from
Ceylon a specimen of an Acacia which had climbed up the trunk of a
rather large tree, by the aid of tendril-like, curved or convoluted
branchlets, arrested in their growth and furnished with sharp
recurved hooks.
{25} As far as I can make out, the history of our knowledge of
tendrils is as follows:- We have seen that Palm and von Mohl observed
about the same time the singular phenomenon of the spontaneous
revolving movement of twining-plants.
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