302 THE BIOLOGY OF FLOWERING PLANTS 



of leaf nature when simple, and when branched it is a shoot 

 bearing leaves (Fig. 44). In some plants, e.g. Ampelopsis 

 Veitchiiy Glaziovia hauhinoides, the tips of the tendrils instead 

 of twining round the support apply themselves to solid 

 surfaces and then form little sucker-like organs, which make 

 an extremely close union ; the stimulus of contact produces 



Fig. 46. — I, Hook tendrils (sympodial branches) of Ancistrocladus 

 Vahlii ; one grasping a support has become thickened ; 2, Root tendrils 

 of Dissochceta sp. Nat. size. (After Treub.) 



a very peculiar result in this case. In some cases shoot 

 tendrils have the form of thorns, and may grip a support, 

 though they do not twine round it ; they show subsequent 

 great thickening ; Strychnos nux-z'omica is an example. 



Root tendrils are rare, and are not very sensitive. 

 Examples are the aroid Philodendron melanochrysmn and the 

 orchid Vanilla planifolia (Fig. 46). 



