FOOD 53 



all the immediate requirements. In any event, starch 

 is a secondary product, and represents the surplus in 

 the manufacture of primary carbohydrates over imme- 

 diate use. 



The process of photosynthesis is not exactly known, 

 but it is probable that the carbon-dioxide and water 

 form a kind of carbonic acid which is reduced by some 

 means, at first perhaps into formic acid, and this is 

 then reduced to formaldehyde. Then occur a series of 

 changes which, for the present, are unknown, and result 

 finally in the formation of starch. 



But these changes which result in the formation of 

 carbohydrates may be considered as the first stages in 

 the manufacture of proteins. As protoplasm is a proteid, 

 and as it is the protoplasm that grows, wastes, and needs 

 repair, the proteins must be considered indispensable 

 for the welfare of the plant. Now proteins cannot be 

 manufactured out of carbohydrates alone, so other 

 materials are necessary, and these are found in the 

 nitrates, sulphates and phosphates. Thus a plant, given 

 these latter, can from them and the carbohydrates 

 manufacture anywhere in its structure these necessary 

 proteins, the real food of the plant. We must confess, 

 however, that the steps in the formation of proteins are 

 all uncertain, and so it would profit little to attempt to 

 describe them. 



