COMPOUNDS OF NUTRITION 



41 



As a rule forage crops contain a higher percentage of ash 

 than do the grains. These variations pertain not alone to 

 the quantity of ash but to the proportions of compounds 

 which it contains: 



TABLE XII. THE MINERAL COMPOUNDS OP PLANTS AND FEEDING- 

 STUFFS (PER CENT IN THE DRY MATTER) 



These figures show that potash, lime, magnesia, and 

 phosphoric acid are the prominent mineral compounds 

 of the plant ash, and it is with them that we find the 

 important variations. The true grasses differ from the 

 clovers and related plants in containing much less lime 

 and greatly more silica, the phosphoric acid and potash 

 not being greatly unlike in the two cases. As a source of 

 lime, then, the clover hay is superior. Potatoes and roots 

 have an ash richer in potash and poorer in lime than are 



