50 ELEMENTS OF AGRICULTURE 



CHAPTER IX.— Composition of Plants 

 -( Continued ) 



46. Mineral Matters or Ash. — The ashes of plants are 

 made up of a number of elements, which are combined 

 into various compounds. Of \he organic elements, car- 

 bon, oxygen, sulphur, and phosphorus are often found 

 in the ashes of plants and sometimes nitrogen and 

 hydrogen. Besides these elements the ash contains sili- 

 con, chlorine, potassium, sodium, calcium, magnesium, 

 iron, manganese, and minute quantities of several other 

 elements. These elements arc all combined in various 

 ways with each other, none of them being found alone. 



47. Phosphorus. — This element, which is a solid sub- 

 stance, has such a tendency to combine with oxygen that 

 it is never found alone. Ordinary phosphorus must 

 be kept under water to prevent its oxidizing. When 

 phosphorus and oxygen unite, the union produces 

 much heat, and this fact is taken advantage of in the 

 manufacture of matches. Phosphorus is usually 

 found combined with calcium and ox} T gen, in which 

 form it is variously called calcium phosphate, phos- 

 phate of lime, and bone phosphate. This compound 

 makes up a large part of the phosphate deposits of the 

 world. Some form of phosphorus exists in the bodies 

 of all plants and animals, and neither can grow without 

 a supply of this element. The combined phosphorus in 



