20 TWINING PLANTS. Cuar. L 
who found different individuals of Solanum dulcamara 
twining in opposite directions, and these had their 
leaves in each case spirally arranged in the same direc- 
tion. A dense whorl of many leaves would apparently 
be incommodious for a twining plant, and some authors 
assert that none have their leaves thus arranged; but 
a twining Siphomeris has whorls of three leaves. 
If a stick which has arrested a revolving shoot, but 
has not as yet been encircled, be suddenly taken 
away, the shoot generally springs forward, showing 
that it was pressing with some force against the stick. 
After a shoot has wound round a stick, if this be with- 
“drawn, it retains for a time its spiral form; it then 
straightens itself, and again commences to revolve. 
The long, much-inclined shoot of the Ceropegia pre- 
viously alluded to offered some curious peculiarities. 
The lower and older internodes, which continued to 
revolve, were incapable, on repeated trials, of twining 
round a thin stick; showing that, although the power 
of movement was retained, this was not sufficient 
to enable the plant to twine. JI then moved the 
stick to a greater distance, so that it was struck by 
a point 24 inches from the extremity of the penulti- 
mate internode; and it was then neatly encircled 
by this part of the penultimate and by the ultimate 
internode. After leaving the spirally wound shoot for 
eleven hours, I quietly withdrew the stick, and in the 
course of the day the curled portion straightened 
itself and recommenced revolving; but the lower and 
not curled portion of the penultimate internode did 
