24 



PRACTICAL BOTANY. 



length, breadth, and depth (thickness). Accordingly, as 

 one or other, or none, of these dimensions predominates, 

 vegetable forms are said to be linear, as leaf-stalks, includ- 

 ing cylindrical (terete), biangular (two-edged), triangular, 

 quadrangular, etc., fdrms ; plane ovflat, orbicular, elliptic, 

 or ovate, as leaves, etc. ; or solid (stereometrical), as fruits, 

 tubers, etc. 



66, Linear forms differ from one another in ilie shape 

 of their cross-sections (see cuts below, I. a — h). 



straight or 

 slightly- 

 curved lines, 

 and exhibit 



tri- 

 angles 



curved lines, f orbicular, : terete, or cylindrical — Fig.(a) 



and exhibit [ semilunar, : semi-terete (b) 



different i (half-terete) 



faces, I elliptic or oval, : compressed 



which are [ biangular, : two-edged 



f with straight sides : triangled. 



with I '^"'■'^'^ ■ triangidar. 



curved \ ^"^^^f 



lines 1 '^^^^^ 

 ""^-^ L outward 



' with straight sides 



I curved 

 J inward 

 1 curved 



(^outward 



(Uipually the terms triangular and three-aided, as well as quadrangular 

 nadi four-sided, are used indiscrimately.) 



All cross- 

 sections 



are 

 circum- 

 scribed 

 by 



squares 



with 

 curved 

 lines 



(0) 



, (e) 

 ; t/iree-sided. 



(0 

 : square. 

 ; quadrangular. 



^ (^) 

 •.four-sided. 



Cut I. 



67. Flat or plane foems are named from their whole 

 or partial outUne. 



