184 HOOK-CLIMBERS. Cuar. V. 
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, Smelaw 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.* 
* Professor Asa Gray has ex- 
plained, as it would appear, this 
disposed to push into dark crevices 
and away from the light, so that 
difficulty in his review (American 
Journal of Science, vol. xl. Sept. 
1865, p. 282) of the present work. 
He has observed that the strong 
summer shoots of the Michigan 
rose (Rosa setigera) are strongly 
they would be almost sure to 
place themselves under a, trellis. 
He adds that the lateral shoots, 
made on the following spring, 
emerged from the trellis as they 
sought the light. 
