128 



PLANT LIFE. 



157. Special forms. — Foliage leaves may be modified to 

 serve special purposes without wholly losing their function as 



Fig. 152.— Palmately veined and branched leal of Norway maple. About half natural 

 size. — After Kerner. 



foliage. For example, the petiole may be made sensitive to 

 contact and adapted to wrap about slender objects, like a 

 tendril, as in clematis and JYS* *t 



nasturtium (fig. 154). Such 

 plants are called leaf-climb- 

 ers. 



Fig. 



'53- 



Fig. 153. — Pinnately veined leaf of buckthorn, with looped ribs forming a selvedge. — 

 After Kerner. 



Fig. 154. — Portion of a plant of the dwarf garden-nasturtium (Tropeeolum minus). 

 The long petiole a, a, a of the leaf / is sensitive to contact and has coiled about 

 the support and its own stem, st. z, axillary branch. Natural size. — After Sachs. 



