produced midribs; but beyond this simple fact they have not been
described. Palm and Mohl class these plants with those which bear
tendrils; but as a leaf is generally a defined object, the present
classification, though artificial, has at least some advantages.
Leaf-climbers are, moreover, intermediate in many respects between
twiners and tendril-bearers. Eight species of Clematis and seven of
Tropaeolum were observed, in order to see what amount of difference
in the manner of climbing existed within the same genus; and the
differences are considerable.

CLEMATIS.--C. glandulosa.--The thin upper internodes revolve, moving
against the course of the sun, precisely like those of a true twiner,
at an average rate, judging from three revolutions, of 3 hrs. 48 m.
The leading shoot immediately twined round a stick placed near it;
but, after making an open spire of only one turn and a half, it
ascended for a short space straight, and then reversed its course and
wound two turns in an opposite direction. This was rendered possible
by the straight piece between the opposed spires having become rigid.
The simple, broad, ovate leaves of this tropical species, with their
short thick petioles, seem but ill-fitted for any movement; and
whilst twining up a vertical stick, no use is made of them.
Nevertheless, if the footstalk of a young leaf be rubbed with a thin
twig a few times on any side, it will in the course of a few hours
bend to that side; afterwards becoming straight again. The under
side seemed to be the most sensitive; but the sensitiveness or
irritability is slight compared to that which we shall meet with in
some of the following species; thus, a loop of string, weighing 1.64
grain (106.2 mg.) and hanging for some days on a young footstalk,
produced a scarcely perceptible effect. A sketch is here given of
two young leaves which had naturally caught hold of two thin