18 THE VITAT- lUNCTIONS. 



immersing the whole surface of another carrot in 

 the fill id, with the exception of the extremity of 

 the root, which was raised so as to be above the 

 surface, no absorption whatever took place. Plants 

 having a fusiform, or spindle-shaped root, such as 

 the carrot and the radish, are the best for these ex- 

 periments. 



In the natural progress of growth, the roots are 

 constantly shooting forwards in the direction they 

 liave first taken, whether horizontally, or down- 

 wards, or at any other inclination. Thus they con- 

 tinually arrive at new portions of soil, of which the 

 nutritive matter has not yet been exhausted ; and 

 as a constant relation is preserved between their 

 lateral extension and the horizontal spreading of 

 the branches, the greater part of the rain which 

 falls upon the tree, is made to drop from the leaves 

 at the exact distance from the trunk, where, after 

 it has soaked through the earth, it will be received 

 by the extremities of the roots, and readily sucked 

 in by the spongioles. We have here a striking in- 

 stance of that beautiful correspondence, which has 

 been established between processes belonging to 

 different departments of nature, and which are 

 made to concur in the production of such remote 

 eftects, as could never have been accomplished 

 without these preconcerted nnd harmonious adjust- 

 ments. 



The spongioles, or absorbing extremities of the 

 roots, are constructed of ordinary cellular or spongy 

 tissue ; and they imbibe the fluids, which are in 

 contact with them, partly by capillary action, and 

 ])artly, also, by what has been termed a lii/gro- 

 scopic power. But though these principles may 



