132 TENDRIL-BEARERS. Cuap. IV. . 
a half; but in one case, in which a tendril depended at 
an angle of 45° beneath the horizon, the uprising took 
two hours; in half an hour afterwards it rose to 23° 
above the horizon and then recommenced revolving. 
This upward movement is independent of the action of 
light, for it occurred twice in the dark, and on another 
occasion the light came in on one side alone. The 
movement no doubt is guided by opposition to the 
force of gravity, as in the case of the ascent of the 
plumules of germinating seeds. 
A tendril does not long retain its revolving power ; 
and as soon as this is lost, it bends downwards and 
contracts spirally. After the revolving movement 
has ceased, the tip still retains for a short time its 
sensitiveness to contact, but this can be of little or no 
use to the plant. 
Though the tendril is highly flexible, and though . 
the extremity travels, under favourable circumstances, 
at about the rate of an inch in two minutes and a 
quarter, yet its sensitiveness to contact is so great that 
it hardly ever fails to seize a thin stick placed in its 
path. The following case surprised me much: I placed 
a thin, smooth, cylindrical stick (and I repeated the 
experiment seven times) so far from a tendril, that 
its extremity could only curl half or three-quarters 
round the stick; but I always found that the tip 
managed in the course of a few hours to curl twice 
or even thrice round the stick. I at first thought 
that this was due to rapid growth on the outside; but 
by coloured points and ineasurements I proved that 
