Any one who will look during windy
weather at twining plants will see that they are easily blown from
their support; not so with tendril-bearers or leaf-climbers, for they
quickly and firmly grasp their support by a much more efficient kind
of movement. In those plants which still twine, but at the same time
possess tendrils or sensitive petioles, as some species of Bignonia,
Clematis, and Tropaeolum, it can readily be observed how incomparably
better they grasp an upright stick than do simple twiners. Tendrils,
from possessing this power of grasping an object, can be made long
and thin; so that little organic matter is expended in their
development, and yet they sweep a wide circle in search of a support.
Tendril-bearers can, from their first growth, ascend along the outer
branches of any neighbouring bush, and they are thus always fully
exposed to the light; twiners, on the contrary, are best fitted to
ascend bare stems, and generally have to start in the shade. Within
tall and dense tropical forests, twining plants would probably
succeed better than most kinds of tendril-bearers; but the majority
of twiners, at least in our temperate regions, from the nature of
their revolving movement, cannot ascend thick trunks, whereas this
can be affected by tendril-bearers if the trunks are branched or bear
twigs, and by some species if the bark is rugged.
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