CH. IV, 11] SPECIAL FUNCTIONS OF STEMS 



195 



the axils of small scales which are morphologically leaves, 

 as exemplified in the familiar " Smilax" of the florists. The 

 Butcher's-Broom of Europe is similar in general, but has 

 this further interesting feature, that on the face of the 

 CLADOPHYLL (as such leaf -like branches are called), occurs 

 a small though genuine leaf, bearing in its axil a flower 

 cluster (Fig. 140). The apparent leaves of the common 

 " Asparagus Fern" likewise 

 are branches, of which several 

 occur in the axil of each 

 scale-like leaf. In clado- 

 phylla the stems have be- 

 come foliage without other 

 function. 



FIG. 141. Echinocactus, a 

 typical globular ribbed Cactus. 

 (Originally after Engelmann.) 



FIG. 142. Rhipsalis Houl- 

 letii; X ^. The seeming leaves 

 are flattened stems, morpho- 

 logically equivalent to a form 

 like the Echinocactus of Fig. 

 141, with the ribs reduced to 

 2 and flattened. (From Rilmp- 

 ler, Die Sukkulenten.) 



The functions of foliage and storage are combined in the 

 succulent stems of Cactus and other plants of dry places. 

 Such stems, which store principally water absorbed during 

 the rainy season, become swollen to cylindrical, or even 

 almost globular forms, while the entire leafless surface bears 

 ample chlorenchyma, with stomata through the thick epi- 

 dermis (Fig. 141). Many of these plants possess vertical 



