26 



THE ROOT, OR DESCENDING AXIS. 



Such is the case with the mustard, beet, maple, and most of the Dico- 

 tyledonous plants. In 



123. THE INAXIAL MODE, the primary radicle, proves abortive, never 

 developing into an axial root ; but, growing laterally 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 gen- 

 erally, and of the Cryptogamia. Plants raised from layers, cuttings, 

 tubers, and slips, are necessarily destitute of the axial root. 



FIGS. 26, Maple an axial, ramose root. 27, Parsnip a fusiform root. 28, Turnip a 

 napiform root. 29, Corallorhiza a coralline root. 



124. THE VARIOUS FORMS OF THE ROOT are naturally and conve- 

 niently referred to these two modes of development. The principal 

 axial forms are the ramose, fusiform, napiform, conical. To all these 

 forms the general name, tap-root, is applied. 



125. THE RAMOSE is the \voody tap-root of most trees and shrubs, 

 where the main root branches extensively, and is finally dissolved and 

 lost in multiplied ramifications. 



126. TUBEROUS TAP-ROOTS. In herbaceous plants the tap-root often 

 becomes thick and fleshy, with comparatively few branches. This ten- 

 dency is peculiarly marked in biennials ( 90), 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 



127. THE FUSIFORM (spindle-shaped) root, thick, succulent, tapering 

 downwards, and also for a short space upwards. The beet, radish, gin- 

 seng are examples. 



