CLIMBING PLANTS. 



699 



into the dark clefts and crevices existing in the supporting wall. Several species of 

 the genera Ois^B, Vitis, and Ampelopsis develop adhesive discs. In the Vitis 

 mconstans, a native of Japan and China, and known among gardeners by the name 

 of Oissus VeitMi (figured on the right-hand side of fig. 166), as soon as the tips of 

 the tendrils, which are provided with tiny knobs, come in contact with a hard wall 

 they spread out, just like the toes of a tree-frog. In a very short time disc-like 

 pads are formed from the knobs, and these become cemented to the substratum by 

 means of a sticky fluid mass secreted from the cells of the disc. This cement now 

 holds so fast that on trying to separate the tendril from the substratum it is much 



Fig. 166. -Light-avoiding Tendrils 

 1 Vitis (Ampelopsis) inserta. Vitit inconstant. 



more likely that the tendril -filament will be torn than that the disc will be 

 detached. Vitis Royleana and Ampelopsis hederacea (the Virginian Creeper) also 

 develop these adhesive discs, but here they are not prefigured by knobs on the 

 branches of the tendrils as in Cissus Veitchii] the ends are curved like hooks, and 

 are barely thickened. As soon as they reach the hard wall the tendril-branches 

 diverge, spread out on it laterally, and arrange themselves at definite intervals 

 in the most advantageous manner. Within two days the curved apices thicken and 

 turn crimson, and in another two days the discs are complete, and the tendrils are 

 cemented by them to the wall. These plants can climb up smooth walls, and even 

 planed wood, glass, and smooth, polished iron are not rejected as substrata. 



Bignonia capreolata, and Vitis (Ampelopsis) inserta (whose tendrils are repre- 

 sented in fig. 166 1 ) behave differently from the three tendril-plants just mentioned. 

 Here the curved tips of the tendrils, growing towards the wall, seek the crevices 



