BOTANY. 



103 



mechanically in the soil and retain it in its position, secondly 

 to absorb from the soil those inorganic elements which are 

 necessary for its food. The general direction of the root is 

 downwards ; but the roots of various plants grow at all angles 

 from the horizontal to the perpendicular : the principal perpen- 

 dicular axis is called the tap root. The number and extent of 

 the roots must correspond with those of the stalk and leaves 

 of the plants, in order to supply their demand of food from the 

 soil. 



Roots do not usually extend to great depths, but keep 

 within the limit of that portion of soil which supplies their 

 proper nutriment. Roots are distinguished from stems and 

 branches by the absence of stomata, buds and pith, and by 

 the presence of absorbing fibres. 



The stock, or main body of the root, sends off i\\Q fibrils, or 

 minute, slender branches of the root, the delicate, tender 

 extremities of the fibrils are called spongioles: these arc the 

 growing points, and the organs which absorb from the soil the 

 earthy part of the food of all plants. If some trees, as the 

 willow or currant, be inverted in the soil, the branches are 

 changed to roots, while the roots put forth leaves in the air, 

 and the plant grows. 



Roots are of several different forms, which have received 

 Fi s- llt specific names for the sake 



of convenience. 



Ramose, or branching 

 roots, are those which send 

 :off many ramifications in 

 various directions, like the 

 branches of a tree: such 

 are the roots of the oak 

 and elm. Fig. 1 1 . 



