ISO ROOT. SPONG10LES. [BOOK u. 



CHAPTER V. 



OF THE ROOT. 



IT is the business of the root to absorb nutriment from the 

 soil, and to transmit it upwards into the stem and leaves ; and 

 also to fix the plant firmly in the earth. Although moisture 

 and gaseous matters are, no doubt, absorbed by the epidermis 

 covering the leaves and bark of all plants, yet it is certain 

 that the greater part of their food is taken up by the 

 roots ; which, hence, are not incorrectly considered vegetable 

 mouths. 



But it is not by the whole surface of the root that the 

 absorption of nutriment takes place ; it is the spongioles 

 almost exclusively, and the adjacent surface, to which that 

 office is confided : and hence their immense importance in 

 vegetable economy, the necessity of preserving them in 

 transplantation, and the death that often follows their destruc- 

 tion. This was shown in the following manner, by Senebier : 

 He took a radish, and placed it in such a position that the 

 extremity only of the root was plunged in water : it remained 

 fresh several days. He then bent back the root, so that its 

 extremity was curved up to the leaves : he plunged the bent 

 part in water, and the plant withered soon ; but it recovered 

 its former freshness upon relaxing the curvature, and again 

 plunging the extremity of the root into the water. 



This explains why forest trees, with very dense umbrageous 

 heads, do not perish from drought in hot summers or in dry 

 situations, where the earth often becomes mere dust for a 

 considerable distance from their trunk, in consequence of 

 their foliage turning off the rain ; the fact is obviously that 

 the roots near the stem are inactive, and have little or nothing 

 to do as preservatives of life except by acting as conduits, 



