ELEMENTS OF STRUCTURAL BOTANY. 63 



83. The Root. This organ is called the descending 

 axis of the plant, from its tendency to grow downward 

 into the soil from the very commencement of its devcl- 

 opement. Its chief use is to imhibe liquid nourishment, 

 and transmit it to the stem. You will remember that 

 in our examination of some common seeds, such as 

 those of the Pumpkin and Bean (Figs. 67-71), we found 

 at the junction of the cotyledons a small pointed pro- 

 jection called the radicle. Now, when such a seed is 

 put into the ground, under favourable circumstances of 

 warmth and moisture, it begins to grow, or germinate, 

 and the radicle, which in reality is a minute stem, not 

 only lengthens, in most cases, so as to push the cotyle- 

 dons upvrards, but developes a root from its lower ex- 

 tremity. All seeds, in short, when they germinate, 

 produce roots from the extremity of the radicle, and 

 roots so produced ax'e called primary roots. 



84. There are two well-marked ways in which a pri- 

 mary root may develope itself. It may, by the down- 

 ward elongation of the radicle, assume the form of a 

 distinct central axis, from the sides of which branches 

 or fibres are given off, or root-fibres may spring in a 

 cluster from the end of the radicle at the very 

 commencement of growth. If the root grow 

 in the first way, it will be a tap-root (Fig. 93), 

 examples of which are furnislied by the Car- 

 rot, the Mallow, and the Bean ; -if in the sec- 

 ond way, it will be a nhron.-i root, examples of 

 which are furnished by the Buttercup (Fig. 1) 

 and by the entire class of Mouocotyledcnous 

 or Endogenous plants. 



86. Tap-roots receive different names, ac- ^iz. 93. 



