for the young internodes of Bignonia Tweedyana and of Hoya carnosa
revolve and twine, but likewise emit rootlets which adhere to any
fitting surface, so that the loss of twining would be no great
disadvantage and in some respects an advantage to these species, as
they would then ascend their supports in a more direct line. {20}



CHAPTER II.--LEAF-CLIMBERS.



Plants which climb by the aid of spontaneously revolving and
sensitive petioles--Clematis--Tropaeolum--Maurandia, flower-peduncles
moving spontaneously and sensitive to a touch--Rhodochiton--
Lophospermum--internodes sensitive--Solanum, thickening of the
clasped petioles--Fumaria--Adlumia--Plants which climb by the aid of
their produced midribs--Gloriosa--Flagellaria--Nepenthes--Summary on
leaf-climbers.

We now come to our second class of climbing plants, namely, those
which ascend by the aid of irritable or sensitive organs. For
convenience' sake the plants in this class have been grouped under
two sub-divisions, namely, leaf-climbers, or those which retain their
leaves in a functional condition, and tendril-bearers. But these
sub-divisions graduate into each other, as we shall see under
Corydalis and the Gloriosa lily.

It has long been observed that several plants climb by the aid of
their leaves, either by their petioles (foot-stalks) or by their