S8 



THE PHYSIOLOGY OF PLANTS 



If we compare with these values the most perfect of artificial 

 manures of organic origin, guano, we find that it contains — 



Of the pure mineral manures, which only contain a few of 

 the nutritive substances, the percentage can be gathered from 

 their advertisements.. 



In stable manures, however, the animal excrements do not 

 form the chief mass, but the latter is formed by the substance 

 which serves as medium of absorption or litter. The latter 

 generally consists of straw, so we append an analysis of straw 

 and of other substances which are used for the same pur- 

 pose, such as pea-stalks, dry leaves, and fresh leaves of pine 

 or fir : ^ — 



' It cannot be considered the object of this book to fully discuss all the 

 materials used as manures, although the practical importance of that subject 

 is fully recognised. But we are here only concerned in illustrating the nature 



