112 TENDRIL-CLIMBERS [CH. 



where the peduncle hooks over a branch ; in both cases 

 the hook retains its hold, long after the leaf or inflores- 

 cence has dropped off. Similar hook-tendrils are formed 

 by peduncles or branches in Ancistrocladus, Artabotrys, 

 Luvunga, Olax, Hugonia, and Strychnos. 



Still more remarkable are the after-effects of the con- 

 tinued contact stimulus at the tips of the tendrils of many 

 species of Ampelopsis, Vitis, and Bignonia, which attach 

 themselves to rocks, walls or the rough bark of trees. The 

 phenomenon can be readily observed in the Virginian 

 Creeper (Fig. 50). The delicate tips of the tendrils swell 

 into fleshy discs, which fit and glue themselves into the 

 interstices of the support, and remain attached for long 

 after the season of their formation, the rest of the tendril 

 throwing itself into woody, elastic, spring-like contractions 

 or coils. 



The climbing of many Bignonice is effected by triple 

 hooks, like bird's claws, which are the three reduced 

 terminal leaflets of one of the pinnate leaves. These 

 hooks are curved and sharp pointed and cling to rough 

 surfaces : they and the tendril they terminate are sensitive 

 to contact. In some of these Bignonice delicate adherent 

 roots are also formed from the same node which bears 

 these tendrils, and since the tendrils coil round a stick and 

 the claws hook over the tendril when thus brought round, 

 we get very complex adaptations brought into play. 



Nor is this all, for, as Darwin showed, some species of 

 Bignonia (e.g. B. Tweedyana) combine with the above the 

 power of twining also, whence we may have four methods 

 of climbing twining, root-climbing, tendril and hook- 

 climbing going on simultaneously in one and the same 

 plant. Tendrils are normally quite smooth, but cases occur 

 where stiff hairs lodes, Serjania, Paullinia or even re- 

 curved hooks species of Desmodium, Acacia, Ccesalpinia 



