CLIMBING PLANTS. 697 



fresh, nutating tendrils, and so may still succeed in grasping some projecting twig 

 in the neighbourhood upon which it can climb. The paths traversed by such 

 tendril-bearing stems are therefore often wound oddly hither and thither, but the 

 stem always follows the periphery of the bush or tree-crown which it has selected, 

 and the inner branches of these supports are never interwoven by it. Plants 

 whose tendril-bearing stems ramify strongly may invest the whole tree over which 

 they grow with an actual mantle, and if the climber in question has large leaves, 

 it may be quite impossible to determine from outside what species of plant has 

 become thus enveloped. 



The account given above deals only with such phenomena as are displayed by 

 all tendril-climbers in common; but in individual cases there are innumerable special 

 contrivances, which it would be impossible to describe in detail in the limits of this 

 book, and I must therefore be content with enumerating some of the most striking 

 that have been observed. 



First, it has been pointed out that in many cases, for example, in the tropical 

 passion-flowers, not only the young, extended tendrils, but also the whole shoot-apex 

 revolve in circles thus widening the space traversed by the tendrils, and increasing 

 the probability of meeting with a support. If the tendrils are forked, each of the 

 two branches performs its particular oscillations, as can be seen, for instance, in the 

 tendrils of the grape-vine. The period of revolution, taken by a nutating tendril, 

 varies very much according to the species. Cobcea scandens takes only 25 minutes, 

 Passiflora sicyoides 30-46 minutes, and Vitis vinifera 67 minutes for a revolution. 

 The rapidity with which the tendrils curve in consequence of the pressure exercised 

 on them by a foreign body which acts as a stimulus also varies very much with the 

 species. In Cyclanthera pedata the curvature commences 20 seconds after contact 

 with a hard stick; in passion-flowers (e.g. Passiflora gracilis and P. sicyoides) after 

 the lapse of about half a minute, in Cissus discolor after 4-5 minutes. If the stick 

 with which the tendril is in contact is removed, the curved portion straightens out 

 again. If it is left in contact, the curvature proceeds uniformly. In Cyclanthera 

 pedata the first complete coil around the support is accomplished in 4 minutes, in 

 others, on the other hand, it may take several hours, or even 1-2 days. Usually 

 the tendril is not content with a single coil, but forms several of them. The coils 

 are closely pressed to the prop, and in their growth adapt themselves like a plastic 

 mass to all its projections and depressions; the substance of the tendril even pene- 

 trates into the small clefts and crevices, and when the tendril is detached from its 

 substratum, an actual cast of all the inequalities of the support can be seen on its 

 contact-surface. In many species, e.g. in Hanbwrya mexicana, peculiar callus-like 

 growths arise here. The ends of the tendrils, as already stated, are curved like a 

 hook so as to more easily grasp the object to which their circling movement brings 

 them. In many species the tendrils terminate in actual claws. The tendrils of 

 Cobcea scandens, a native of Mexico, but frequently grown as a decorative plant in 

 our conservatories, are specially elegant. They are leaf- or midrib-tendrils, and 

 divide repeatedly in the most beautiful manner. Each of the ultimate branches 



