SECTION 5.] 



ROOTS. 



35 



and their soft and tender tips liarden. From (his period, therefore, until 

 growth begins anew the next spring, is the best time for transplanting; 

 especially for trees and shrul)s. 



73. The absorbing surface of young roots is much increased by the for- 

 mation, near their tips, of Root-hairs (Fig. 81, 82), which are delicate 



tubular outgrowths from the surface, through the delicate walls of which 

 moisture is promptly imbibed. 



74. Fleshy Roots are those in which the root becomes a storehouse of 

 nourishment. Typical roots of this kind are those of such biennials as the 

 turnip and carrot ; in which the food created in the first season's vege- 

 tation is accumulated, to be expended the next season in a vigoroils growth 

 and a rapid development of flowers, fruit, and seed. By the time the seed 

 is matured tlic exhausted root dies, and with it the whole plant. 



75. Fleshy roots may be single or multiple. The single root of the 

 commoner biennials is the primary root, or tap-root, which begins to 

 thicken in tlie seedhng. Names are given to its shapes, such as 



Conical, when it thickens most at tiie crown, or where it joins the stem, 

 and tapers regularly downwards to a point, as in the Parsnip and Carrot 

 (Fis. 84) ; 



Turnip-shaped or napiform, when greatly tiiiekened above, but abruptly 

 becoming slender below ; as the Turnip (Fig. 83) ; and 



Fig. 86. Sweet-Potato plant forming thickened roots. Some in tlie middle are 

 just beginning to thicken; one at the left has grown more; one at the right is stiU 

 larger. 



Fie. 87. Fa.sciclcd fu.siform roots of a Dahlia ; a, a, buds on base of stem. 



