MANURES. 39 



portant to a given plant. As a result of these inquiries, 

 plants have been divided into four classes, according as 

 one or another inorganic element is found to predominate 

 in their ashes. 



1. jSilex Plants. Those that abound m silica, as the 

 grasses, equisetums, etc. 



2. Alkali Plants. Those that contain alkaline salts in 

 large proportions, as beets, potatoes, and the vine. Pot- 

 ash salts are necessary to all land plants, especially to 

 conifers and other trees, while soda salts, particularly its 

 chloride, to all marine plants. 



3. Lime Plants. Those that contain the earths, espe- 

 cially lime and magnesia, as clover, peas, beans, etc. 



4. Phosphorus Plants. Those that contain the phos- 

 phates, as the cereals, wheat, corn, rye, oats, fruits. 

 All food-bearing plants contain more or less of the phos- 

 phates in their ashes, as cabbages, turnips, onions, etc. 



Phosphates of lime and potash are the inorganic sub- 

 stances most likely to be needed in soils, as they are soon- 

 est exhausted. The salts of lime, as the carbonate and 

 sulphate, after these, are generally next valuable. Lime, 

 however, is injurious to heaths. Nitrogenous manures, so 

 generally serviceable, are injurious to conifers and stone 

 fruits. (Lindley.) 



An analysis of stable manure shows it to contain all the 

 elements required for the food of plants ; every part of it 

 has been formed of vegetable products, and is ready when 

 rendered soluble to enter into and minister again to their 

 growth. 



The decayed parts of any plant rendered soluble, and 

 likewise its ashes, are among the best manures for plants 

 of its own species. Vineyards have been kept fertile by 

 digging into the soil the fresh prunings of the vines, and 

 indeed are said to have increased in richness from the 

 slight manuring their own leaves afford. So forests, we 

 know, are enriched by the falling leaves. 



