ADAPTATION TO WATER 



163 



2. The virgate jorm. The leaves either fall off early or are 

 reduced to functionless scales. The stems are thin, erect, and 

 rod-like, and are often greatly branched. They usually possess 

 a thick cuticle and much palisade tissue, and the stomata are 

 often sunken in longitudinal furrows. This type is characteristic 

 of Genista and many of its relatives. It is found also in Ephedra, 

 many species of Polygonum, Lygodesmia, etc. 



3. The rush form. In many species of Juncus, Heleocharis, 

 Scirpus, and other Cyperacece the stem is nearly or completely leaf- 



FiG. 53. A stem succulent, Cactus viviparus. 



less, and it is cylindrical and unbranched. It usually possesses a 

 thick cuticle and several rows of dense palisade tissue. 



4- The cladophyll form. In Asparagus the leaves are reduced 

 to mere functionless scales, and their work is assumed by the 

 small needle-shaped branches. 



5. The flattened form. This is a variation of the jirocoding 

 type. The place of the scale-like leaves is taken l)y rlndophylis, 

 which are more or less flattened and leaf-like branches. Ruscus 

 is a familiar example of this form. 



