tem from south through west to south again. Other
plants, e.g. Phaseolus, revolve in the opposite direction.), on which
most climbers depend, is inherent, though undeveloped, in almost every
plant in the vegetable kingdom." ("Climbing Plants", page 205.)

In the "Origin" (Edition I. page 427, Edition VI. page 374.) Darwin
speaks of the "apparent paradox, that the very same characters are
analogical when one class or order is compared with another, but give
true affinities when the members of the same class or order are compared
one with another." In this way we might perhaps say that the climbing
of an ivy and a hop are analogical; the resemblance depending on the
adaptive result rather than on community of blood; whereas the relation
between a leaf-climber and a true tendril-bearer reveals descent. This
particular resemblance was one in which my father took especial delight.
He has described an interesting case occurring in the Fumariaceae.
("Climbing Plants", page 195.) "The terminal leaflets of the
leaf-climbing Fumaria officinalis are not smaller than the other
leaflets; those of the leaf-climbing Adlumia cirrhosa are greatly
reduced; those of Corydalis claviculata (a plant which may be
indifferently called a leaf-climber or a tendril-bearer) are either
reduced to microscopical dimensions or have their blades wholly aborted,
so that this plant is actually in a state of transition; and finally in
the Dicentra the tendrils are perfectly characterized."

It is a remarkable fact that the quality which, broadly speaking, forms
the basis of the climbing habit (namely revolving nutation, otherwise
known as circumnutation) subserves two distinct ends. One of these is
the finding of a support, and this is common to twiners and tendrils.
Here the value ends as far as tendril-climbers are concerned, but in
twiners Darwin believed that the act of climbing round a support is a
continuation of the revolving movement (circumnutation). If we imagine a
man swinging a rope round his head and if we suppose the rope to strike
a vertical post, the free end will twine round it. This may serve as
a rough model of twining as explained in the "Movements and Habits
of Climbing Plants". It is on these points--the nature of revolving
nutation and the mechanism of twining--that modern physiologists differ
from Darwin. (See the discussion in Pfeffer's "The Physiology of Plants"
Eng. Tr. (Oxford, 1906), III. page 34, where the literature is given