It may, however, be suspected from what follows, that
these shoots in some cases tend to avoid the light. The few hook-
climbers which I have observed, namely, Galium aparine, Rubus
australis, and some climbing Roses, exhibit no spontaneous revolving
movement. If they had possessed this power, and had been capable of
twining, they would have been placed in the class of Twiners; for
some twiners are furnished with spines or hooks, which aid them in
their ascent. For instance, the Hop, which is a twiner, has reflexed
hooks as large as those of the Galium; some other twiners have stiff
reflexed hairs; and Dipladenia has a circle of blunt spines at the
bases of its leaves. I have seen only one tendril-bearing plant,
namely, Smilax aspera, which is furnished with reflexed spines; but
this is the case with several branch-climbers in South Brazil and
Ceylon; and their branches graduate into true tendrils. Some few
plants apparently depend solely on their hooks for climbing, and yet
do so efficiently, as certain palms in the New and Old Worlds. Even
some climbing Roses will ascend the walls of a tall house, if covered
with a trellis. How this is effected I know not; for the young
shoots of one such Rose, when placed in a pot in a window, bent
irregularly towards the light during the day and from the light
during the night, like the shoots of any common plant; so that it is
not easy to understand how they could have got under a trellis close
to the wall.
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