ALBUMEN AND STARCH. 81 



phate of lime is required, and only a small 

 quantity of magnesia. 



To make this subject intelligible and of great 

 value to the farmer, we shall give tables show- 

 ing the composition of the grain and straw, and 

 the roots and tops of the plants commonly culti- 

 vated. A study of these tables will amply 

 repay him, by giving accurate knowledge of the 

 composition of plants, which is the only key to 

 what is needed in manures to produce them. It 

 will also, in connection with a knowledge of the 

 constituents of his soil, enable him to understand 

 the philosophy of a rotation of crops, and to select 

 that which is best suited to his land, and the 

 manures at his command ; and especially enable 

 him to estimate the value of the waste products 

 of his farm, and to apply them to the best advan- 

 tage. 



All plants and seeds cultivated for food con- 

 tain albumen and starch ; the starch and sugar 

 are produced in the plant from carbonic acid and 

 water; the albumen and gluten result from the 

 mutual action of the same compounds, together 

 with ammonia, or nitric acid, and certain sulphates 

 and phosphates, but the manner by which this 

 is effected is a mystery that has not been fully 

 solved by the most laborious investigation. 

 Plants are valuable as food in proportion to the 

 amount of albumen and starch they contain. 



