a considerable time round a support, it permanently retains its
spiral form even when the support is removed.

When a tall stick was placed so as to arrest the lower and rigid
internodes of the Ceropegia, at the distance at first of 15 and then
of 21 inches from the centre of revolution, the straight shoot slowly
and gradually slid up the stick, so as to become more and more highly
inclined, but did not pass over the summit. Then, after an interval
sufficient to have allowed of a semi-revolution, the shoot suddenly
bounded from the stick and fell over to the opposite side or point of
the compass, and reassumed its previous slight inclination. It now
recommenced revolving in its usual course, so that after a semi-
revolution it again came into contact with the stick, again slid up
it, and again bounded from it and fell over to the opposite side.
This movement of the shoot had a very odd appearance, as if it were
disgusted with its failure but was resolved to try again. We shall,
I think, understand this movement by considering the former
illustration of the sapling, in which the growing surface was
supposed to creep round from the northern by the western to the
southern face; and thence back again by the eastern to the northern
face, successively bowing the sapling in all directions. Now with
the Ceropegia, the stick being placed to the south of the shoot and
in contact with it, as soon as the circulatory growth reached the
western surface, no effect would be produced, except that the shoot
would be pressed firmly against the stick. But as soon as growth on
the southern surface began, the shoot would be slowly dragged with a
sliding movement up the stick; and then, as soon as the eastern
growth commenced, the shoot would be drawn from the stick, and its
weight coinciding with the effects of the changed surface of growth,
would cause it suddenly to fall to the opposite side, reassuming its