80 STEUCTUKAL BOTANY. [67, 68. 



the primary, simple radicle, in growing, extends itself 

 downward in a main body more or less branched, 

 continuous with the stem, and forms the permanent 

 root of the plant. Such is the case with the Maple, 

 Mustard, Beet, and most of the Dicotyledonous Plants 

 ( 183). 



201. Secondly, the DIFFUSE development is that 

 where the primary radicle proves abortive, never 

 developing into an axial root ; but, growing lat- 

 erally only, it sends out little shoots from its sides, 

 which grow into long, slender roots, nearly equal 

 in value, none of them continuous with the stem. 

 Of this nature are the roots of all the Grasses, 

 the Lilies, and the Monocotyledons generally, and of 

 the Cryptogamia. Plants raised from layers, cuttings, 

 tubers, and slips are necessarily destitute of the axial 

 root. 



202. The various forms of the root are naturally 

 and conveniently referred to these two modes of devel- 

 opment. The principal axial forms are the ramous, 

 fusiform, napiform, and conical. To all these forms 

 the general name tap-root is applied. The ramous is 

 the woody tap-root of most trees and shrubs, where 

 the main root branches extensively, and is finally dis- 

 solved and lost in multiplied ramifications. 



203. Tuberous tap-roots. In herbaceous plants 

 the tap-root often becomes thick and fleshy, with com- 

 paratively few branches. This tendency is peculiarly 

 marked in biennials ( 41), where the root serves as a 

 reservoir of the superabundant food which the plant 

 accumulates during its first year's growth, and keeps 

 in store against the exhausting process of fruit-bearing 

 in its second year. Such is the Fusiform (spindle- 



