one or two turns in an opposite direction. The reversal of the
curvature occurred at any point in the stem, even in the middle of an
internode. Had I not seen this case, I should have thought its
occurrence most improbable. It would be hardly possible with any
plant which ascended above a few feet in height, or which lived in an
exposed situation; for the stem could be pulled away easily from its
support, with but little unwinding; nor could it have adhered at all,
had not the internodes soon become moderately rigid. With leaf-
climbers, as we shall soon see, analogous cases frequently occur; but
these present no difficulty, as the stem is secured by the clasping
petioles.

In the many other revolving and twining plants observed by me, I
never but twice saw the movement reversed; once, and only for a short
space, in Ipomoea jucunda; but frequently with Hibbertia dentata.
This plant at first perplexed me much, for I continually observed its
long and flexible shoots, evidently well fitted for twining, make a
whole, or half, or quarter circle in one direction and then in an
opposite direction; consequently, when I placed the shoots near thin
or thick sticks, or perpendicularly stretched string, they seemed as
if constantly trying to ascend, but always failed. I then surrounded
the plant with a mass of branched twigs; the shoots ascended, and
passed through them, but several came out laterally, and their
depending extremities seldom turned upwards as is usual with twining
plants. Finally, I surrounded a second plant with many thin upright
sticks, and placed it near the first one with twigs; and now both had
got what they liked, for they twined up the parallel sticks,
sometimes winding round one and sometimes round several; and the
shoots travelled laterally from one to the other pot; but as the
plants grew older, some of the shoots twined regularly up thin