16 



THE STEM 



elided with the plant's genealogy or with the way in 



which it has been obliged to live. 



42. The stem may be simple or branched. A simple 



stem usually grows from the terminal bud, and side 



branches either do 

 not start, or, if they 

 start, they soon per- 

 ish. Mulleins (Fig. 

 22) are usually sim- 

 ple. So are palms. 



43. Branched 

 stents may be of very 

 different habit and 

 shaj)e. Some stem 

 systems are narrow 

 and erect: these are 

 said to be strict. 

 Others are dif- 

 fuse, open, branchy, 

 twiggy. 



44. STEMS vs. 

 ROOTS. Roots 

 sometimes grow 

 above ground (31- 

 33) ; so, also, stems 

 sometimes grow un- 

 derground, and they are then known as subterranean stems, 

 rhizomes, or rootstocks (Fig. 23). 



45. Stems normally bear leaves and buds, and thereby 

 are they distinguished from roots. The leaves, however, 

 may be reduced to mere scales, and the buds beneath 

 them maybe scarcely visible. Thus the "e3'es" on an Irish 

 potato are cavities with a bud or buds at the bottom (Fig. 

 24). Sweet potatoes have no evident "eyes" when first 

 dug (but they may develop buds before the next growing- 



20. Orape vine climbing on a tree. Illustrating 

 two kinds of stems. 



