54 



Elementary Botany 



called a caulis ; when woody and perennial, a trunk ; and when 

 jointed, as in Grasses, a culm. 



Generally stems are able to support themselves in an up- 

 right position, and are erect ; if they trail on the ground they 



are prostrate ; if, whilst thus 

 reclining, they rise towards 

 their extremities, they are de- 

 cumbent ; or if they gradually 

 rise from near the base, as- 

 cending. 



Some stems are climbing. 



Fig. 76.— I. Section of triangular stem. 

 II. Section of square stem. III. Section 

 of five-ribbed stem. 



attaching themselves to some object of support either by root- 

 lets (as in the Ivy), or by tendrils (as in the Passion Flower and 

 Sweet Pea). At other times they are twining around the 

 object of support (as in the Bind- weed and Hop, fig. 77). 



Fig. 77. — I. Stem of Convolvulus arvensis twining to the left. 11. Stem of 

 Hop twining to the right 



There are certain terms which are applied to various forms 

 of stems, some of which describe the aerial or above ground, 

 and others the subterranean stems. 



