Roots 109 



is a foot, or even an inch or a half-inch away, is of no 

 use, except so far as it may be dissolved by water. The 

 roots can do nothing with it unless some part of them, 

 fibers or hairs, are near enough to get hold of it and press 

 close to it, as the lichen adheres to the rock. 



And it is this which makes it so important that a soil 

 should be not only finely ground, but well mixed, so that 

 all the ingredients may be within reach of the roots of 

 each plant. 



Most soils distinguished for their fertility contain a large 

 proportion of fine matter, and to this is largely due the 

 extraordinary productiveness of some of the lands of Ohio, 

 which have borne heavy crops of wheat and maize for 

 sixty years in succession. A considerable part of the soil 

 here consists of particles which measure from the five- 

 hundredth to the thousandth part of an inch across. The 

 same thing is to be observed in the black earth of Russia, 

 and again in the mud brought down by the Nile and other 

 rivers: all are distinguished for the fineness of their par- 

 ticles and their thorough mixture. 



Why is it that a block of granite is able to support 

 only a few lichens and mosses } Chiefly because it is a 

 block, into which roots cannot penetrate. It would not 

 make a really fertile soil even if it were crushed into 

 coarse gravel, but it would grow more than it does now; 

 and if it were ground to fine powder and kept well watered, 

 it would grow even corn — not perhaps good crops, though 

 even granites differ in fertility, but still corn — whereas not 

 a stalk can spring up while the granite remains a block, no 

 matter how diligently it be watered. 



By way of testing this point, an experiment was made 

 with some barley sown in a soil consisting of pure feldspar. 



