LECT. VI.] THE STEM. ITS DIRECTION. 245 



erect stem,, derived from the character of the 

 line it produces from the base 

 to the apex. An erect stem is 

 a. Straight (strictus, rectus, 

 rectilineus) (fig. a), when it has 

 no natural curve in any portion 

 of its length, however] thickly 

 branched it may be ; as r for ex- 

 ample, that of the Silver Fir, 

 Pinus Picea (a), among trees ; 

 and of Spear Mint, Men t ha vi- 

 ridis, among herbaceous plants. 



b. Flexuose (flexuosus) 

 (fig. b), when it is naturally 

 a regular zigzag, so as to form 

 alternate obtuse angles from 

 right to left, and from left to 

 right * ; as in Box-leaved 

 Staff-tree, Celastrus buxifolius 

 (#) ; and common Birthwort, 

 Aristolochia Clematitis. 



c. Tortuous (tortuosus), 

 when it is curved or writhed 

 in different directions, but 

 not regularly as in the flex- 

 nose stems. 



* " Flexuosus, secundum articulos horsum vorsum flexui ; 

 Ptclea." Phil. But. 82. 4. 



R3 



