76 



STRUCTURAL BOTANY. 



venient terms, denoting, the former the presence, and the latter 

 the absence of the caulis or aerial stem. 



224. THE CULM is the stem of the Grasses and the Sedges, 

 generally jointed, often hollow, rarely becoming woody ; as in 

 Cane and Bamboo. 



8 B E 



256, 8, Spruce. B, Beech. E, Elm ; to illustrate excurrent and solvent axis. 



225. THE TRUNK is the name of the peculiar stems of arbor- 

 escent plants. It is the central column or axis which supports 

 their branching tops and withstands the assaults of the wind by 

 means of the great firmness and strength of the woody or lig- 

 neous tissue with which it abounds. The trunk is usually seen 

 simple and columnar below, for a certain space, then variously 

 dividing itself into branches. Here it is cylindrical, straight, 

 and erect, as in the Forest Pine; prismatic often, as in the Gum- 

 tree ; gnarled and curved, as in the Oak ; or inclined far over its 

 base, as in the Sycamore. 



226. In dividing itself into branches we observe two general 

 modes, with their numerous variations, strikingly characterizing 



