twining in opposite directions, and these had their leaves in each
case spirally arranged in the same direction. 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 After a shoot has wound round a stick, if this be withdrawn,
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 previously 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. I then moved the stick to a
greater distance, so that it was struck by a point 2.5 inches from
the extremity of the penultimate 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 not move, a
sort of hinge separating the moving and the motionless part of the
same internode. After a few days, however, I found that this lower
part had likewise recovered its revolving power. These several facts
show that the power of movement is not immediately lost in the
arrested portion of a revolving shoot; and that after being
temporarily lost it can be recovered. When a shoot has remained for