Of what use would it be, if an old and full-grown tendril,
arising from the lower part of a shoot, were to retain its power of
clasping a support? This would be of no use; and we have seen with
tendrils so many instances of close adaptation and of the economy of
means, that we may feel assured that they would acquire irritability
and the power of clasping a support at the proper age--namely, youth-
-and would not uselessly retain such power beyond the proper age.
CHAPTER V.--HOOK AND ROOT-CLIMBERS.--CONCLUDING REMARKS.
Plants climbing by the aid of hooks, or merely scrambling over other
plants--Root-climbers, adhesive matter secreted by the rootlets--
General conclusions with respect to climbing plants, and the stages
of their development.
Hook-Climbers.--In my introductory remarks, I stated that, besides
the two first great classes of climbing plants, namely, those which
twine round a support, and those endowed with irritability enabling
them to seize hold of objects by means of their petioles or tendrils,
there are two other classes, hook-climbers and root-climbers. Many
plants, moreover, as Fritz Muller has remarked, {40} climb or
scramble up thickets in a still more simple fashion, without any
special aid, excepting that their leading shoots are generally long
and flexible.
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