74 



PRACTICAL COURSE IN BOTANY 



Fig. 86. — Brauchuu tap 

 root of maple. 



the first kind a single stout prolongation called a taproot 

 proceeds from the lower end of the hypocotyl and continues 

 the axis of growth straight downward, unless turned aside 

 by some external influence. A taproot may be either simple, 

 as in the turnip, radish, and dandelion, 

 or branched, as in most shrubs and 

 trees. In the latter case the main axis 

 is called the primary root, and the 

 branches are secondary ones. 



80. Fibrous and fascicled roots. — 

 Where the main axis fails to develop, 

 as in the corn and grasses generally, 

 a number of independent branches take 

 its place, forming what are known as 

 fibrous roots. Both fibrous and tap- 

 roots may be either hard or fleshy. 

 The turnip and carrot are examples of 

 fleshy taproots, the dahha and rhubarb of fascicled roots. 

 The function of both is the storage of nourishment. The 

 sweet potato is an example of a tuberous root. 



81. Practical importance of this distinction. — The dif- 

 ference between axial and fibrous roots has important bear- 

 ings in agriculture. The first kind, 

 which are characteristic of most dicot- 

 yls, strike deep and draw their nour- 

 ishment from the lower strata of the 

 soil, while the fibrous and fascicled, or 

 radial kinds, as we may call them for 

 want of a better name, spread out near 

 the surface and are more dependent on 

 external conditions. 



82. Roots that grow above ground. — The kinds 

 roots that have just been considered are all subterranean, 

 and bring the plant into relation with the earth, whether for 

 the purpose of absorbing nourishment, or of mechanical sup- 

 port, or, as in the majority of cases, for both. Many plants, 



Fig. 87. — Fibrous root. 



of 



