54 SAG AC/TV AND MORALITY OF PLANTS. 



capreolata, is fairly on the way. Among other well- 

 known leaf- stalk climbers are species of Bignonia, 

 Solanum, Maurandia, Lophospermum, Trop3eolum,etc. 

 The highest degree of specialisation for climbing 

 purposes, however, is the development of tendrils. 

 These may be, and usually are, modifications of 

 stipules, leaves, and branches. Be that as it may, 

 tendrils are organs differentiated to perform a special 

 kind of work for the benefit of the plants possessing 

 them. They may be found in nearly every stage of 

 development, from single to even branched tendrils. 

 All of them, however, are distinguished by their 

 sensitiveness, which reaches its climax, perhaps, in 

 Passiflora gracilis. Some of this class of climbing 

 plants have branched tendrils possessing suckers at 

 their buds, like the well-known Virginian Cree'per 

 {Ampelopsis hederaced). The suckers exude a natural 

 cement, which, however, does not form until the 

 sensitive tendril -tips have first found a good foot- 

 hold. Similar discs for the tendrils to hold on by 

 are developed by Bignonia capreolata, and a species 

 of the Cucumber family. Some plants have tendrils 

 provided with hooks at their tips, like the Cobceas, 

 which they insert in chinks and crevices. All tendril- 

 bearing plants are further remarkable for the help 

 afforded these sensitive organs by the stems. In- 

 stead of being rigid, as we have seen is the case in 

 the first two or three joints of twining plants, the 

 young internodes adopt the opposite plan, and revolve 



