246 AGRICULTURAL CHEMISTRY 



action of the protoplasm and chlorophyl within the plant 

 cells, starch and all other organic compounds are pro- 

 duced from the carbon dioxid of the air and from the 

 water, mineral matter, and nitrogen of the soil. All of 

 the carbohydrates can be produced from starch as was 

 stated in Section 289, which discusses the general rela- 

 tionship existing between the various non-nitrogenous 

 compounds. Fat, as well as other non-nitrogenous com- 

 pounds, is produced from starch. Proteids are produced 

 from amides. By a succession of chemical changes, the 

 amide molecule takes on fatty acid and carbohydrate 

 radicals, and as a result, complex proteids are produced. 

 All of these chemical changes take place within the plant 

 cell ; and, for the production of the various compounds 

 which constitute the dry matter of plants, the essential 

 mineral elements, nitrogen in combination, carbon dioxid 

 and water, are required. 



