54 LEAF-CLIMBERS. Cuap. II. 
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 
Fig. 2. 
A young leaf of Clematis viticella. - 
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 
