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 leaf 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 

 nasturtium (fig. 154). Such 

 plants are called leaf-climb- 

 ers. 



FIG. 154. 



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 (Trofeeolum mimts). 

 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. 



