84 



THE ROOT. 



seed. Such plants send up no lengthened stem during the first 

 summer, but pi'oduce a large tuft of leaves next the ground, and 



proceed to elaborate what they re- 

 ceive from the roots and from the air 

 into organic or nourishing matter, and 

 store it up in the root, in the form of 

 starch, vegetable jelly, and the like. 

 The root enlarges, or becomes fieshy, 

 as this accumulates. In biennials this 

 accumulation generally takes place in 

 the primary or main root, as in the 

 Eadish, Carrot, Beet, &c. This, when 

 only moderately thickened and taper- 

 ing downwards, is a common tof-root : 

 when more enlai'ged and broadest at 

 the crown, or junction with the ex- 

 tremely abbreviated stem, it forms a 

 conical root, like that of the common 

 Beet and Parsnip : when broadest in 

 the middle and tapering to both ends, it is spindle-shaped or fusi- 

 form, as in the Radish (Fig. 138) : when much broader than long, 

 and abruptly contracted below, hke a turnip, it is napiform. Such 

 roots, abounding in nourishment, are appropriated by man for food. 

 The plant itself uses this store for the same purpose. When the 

 vegetation of these biennials is resumed, the following spring, the 

 new shoots, fed by this abundant stock of nourishment provided for 

 them, grow with great vigor, and produce flowers, fruit, and seed 

 almost entirely at its expense ; and this stock being exhausted by the 

 time the seeds are matured, Avhen the cells of the great root will be 

 found to be emptied of their contents and dead, the plant perishes. 



14G. Perennial Roots are those of plants which last year after year. 

 In shrubs and trees the roots themselves live and grow indefinitely ; 

 but in perennial herbs the same roots seldom survive more than a 

 year or two, and a new set is formed annually. Here, also, a store 

 of nourishment for the vigorous commencement of the succeeding 

 year's growth is not unfrequently deposited in the root. The Sweet 

 Potato, the Peony, and the Dahlia (Fig. 139), furnish good illustra- 

 tions of the kind. These roots are generally /os^c/efi or clustered; 

 that is, they consist of a cluster of roots from the base of the stem. 



FIG. 138. Fusiform root of the Radish, with some foliage. 



