The movement of the whole shoot by
the wind and by its rapid growth, would probably be almost equally
efficient as these spontaneous movements, in bringing the petioles
into contact with surrounding objects.
The leaves are of large size. Each bears three pairs of lateral
leaflets and a terminal one, all supported on rather long sub-
petioles. The main petiole bends a little angularly downwards at
each point where a pair of leaflets arises (see fig. 2), and the
petiole of the terminal leaflet is bent downwards at right angles;
hence the whole petiole, with its rectangularly bent extremity, acts
as a hook. This hook, the lateral petioles being directed a little
upwards; forms an excellent grappling apparatus, by which the leaves
readily become entangled with surrounding objects. If they catch
nothing, the whole petiole ultimately grows straight. The main
petiole, the sub-petioles, and the three branches into which each
basi-lateral sub-petiole is generally subdivided, are all sensitive.
The basal portion of the main petiole, between the stem and the first
pair of leaflets, is less sensitive than the remainder; it will,
however, clasp a stick with which it is left in contact.
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