52 PLANTS 



in. Other types of underground storage stems are common. 

 The root-stock differs from the tuber in that it has no slender 

 connecting stem but is thickened throughout its length. It 



FIG. 24. Young shoots of the common cactus, Opuntia, showing the small, 

 conical leaves. These soon disappear. Note that the spines develop in the 

 axils of the leaves. X2/3. 



usually persists from year to year; a new segment consisting 

 of one or more nodes, being added each season. When the 



