10 INTRODUCTION. 



epidermis, enlarge by the addition of fibres to their interior., 

 and are thus said to be Endogenous, or growing inwards. 



.Herbaceous stems have also an epidermis, cellular substance,, 

 fibrous and vascular tissue, and sometimes internal pith. 



The stem of a tree is called its Trunk ; the divisions of the 

 stem are the Branches and Twigs. 



Stems in general may be simple, having no divisions ; or 

 they may be branched. Of the latter there are several kinds. 



A Forked or Dichotomous Stem (Fig. 10.) is when it is regu- 

 larly and repeatedly divided into two, and a flower springs from 

 each fork. 



A Panicled Stem is when branches come oif irregularly, and 

 are themselves irregularly divided, the ultimate divisions bear- 

 ing flowers. 



Two -ranked, when the branches spread in two opposite di- 

 rections. 



Four-ranked, when they spread in four directions. 



With respect to its general direction, the Stem is 



Erect or Upright, when it rises perpendicularly. 



Ascending or Oblique, having an oblique direction. 



Procumbent, lying on the ground. 



Creeping or Repent, running along the ground, and sending 

 down roots from space to space, in the manner of Fig. 2. The 

 Runner (Fig. 11.), is a stem of this kind, which, forming a bud 

 at its extremity, produces a new plant, and then withers. 



Prostrate, lying remarkably flat. 



Clinging (Fig. 12.), holding fast to some other body for sup- 

 port, by means of fibres. 



Climbing or Scandent, ascending on other bodies, either by 

 fibres or by tendrils. 



Twining round other plants or bodies. (Fig. 13.) Some 

 stems twine from left to right, others from right to left. 



Straight, proceeding in a direct course. 



Flexuous or Zig-zag, forming angles from right to left, and 

 the reverse. 



With respect to form, the Stem is 



Round or Cylindrical, when a transverse section is circular, 

 or nearly so. 



Semi-cylindrical, when flat on one side and round on the 

 other. 



