Roots 133 



much larger surface to act upon, and can act more 

 quickly. And this is one reason wliy finely-ground 

 soils are so generally fertile. 



But this is not the only reason ; for, besides drink- 

 ing in the moisture of the soil, with whatever may be 

 dissolved in it, the roots do much dissolving on their 

 own account. And it is for this purpose, apparently, 

 that all, down to the smallest fibre, and even hair, are 

 more or less acid. 



What food comes to them ready dissolved may be 

 brought from a distance from the soil above or below 

 the roots, but it h brought. The particles of soil, on 

 the other hand, do not move, and the roots must go to 

 them, and actually touch them, and that very closely, 

 for the acid to be able to act upon them. A rich 

 morsel which 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, fibres or hairs, are near enough to 

 get hold of it and press close to it, as the hchen 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 consider- 

 able 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 



