STEM. 



19 



152. It often burrows beneath the earth, when it is vulgarly 

 called a creeping root'*. Sometimes the internodes become 

 much thickened, when what are called tubers 11 78 are formed ; 

 or the stem lies prostrate upon the earth, emitting roots from 

 its under side, when it is called a rhizoma, or rootstock 67 . 



153. If it distend underground, without creeping or root- 

 ing, but always retaining a round or oval figure, it is called a 



75 . 



154. All these forms of stem are vulgarly called roots. 



155. No root can have either scales, which are the rudi- 

 ments of leaves, or nodes, which are the rudiments of buds. 

 A scaly root is, therefore, a contradiction in terms. 



156. The ascending axis, or stem, has nodes and internodes. 



157. Nodes are the places where the leaves are expanded 

 and the buds formed. 



158. Internodes are the spaces between the nodes. 



159. Whatever is produced by the evolution of a leaf-bud 

 (164) is a branch. 



160. A spine is the imperfect evolution of a leaf-bud, and 

 is, therefore, a branch. 



161. All processes of the stem which are not the evolutions 

 of leaf-buds, are mere dilatations of the cellular integument of 

 the bark. Such are prickles (61). 



162. In solid form the stem is extremely variable; the fol- 

 lowing are common terms relating to it : 



c 2 



