110 THE ROTHAMSTED EXPERIMENTS. 



Vines' so far as would appear without any special reference to the 

 mews. £ ac |. ^q^ j n th e case f our chief starch- and sugar-yielding 

 crops, the production of those substances is greatly enhanced 

 by the use of nitrogenous manures, it has been suggested 

 that the substance first formed in the chlorophyll-corpuscle 

 from carbon dioxide and water is not starch, but a substance 

 possibly allied to formic aldehyde (CH 2 0), which goes to 

 construct proteid, by combining with the nitrogen and sul- 

 phur absorbed in the form of salts from the soil, or with the 

 nitrogenous residues of previous decompositions of proteid. 

 It is supposed, however, that starch may nevertheless be the 

 first visible product of the constructive metabolism ; since, 

 unless protoplasm were being formed, no starch could be 

 produced. 



This view is partly founded on the consideration of the 

 analogy that would then be established between the forma- 

 tion of starch and that of the carbohydrate — cellulose, which 

 is by some experimenters supposed to be derived directly 

 from protoplasm. 



It is true that such a supposition is at any rate not incon- 

 sistent with the conditions which we have seen to be favour- 

 able for the increased production of starch and sugar in 

 agricultural plants. At the same time, it is admittedly at 

 present little more than hypothesis. It would, indeed, re- 

 quire more evidence than is at present available, to establish 

 such a conclusion ; whilst there are considerations which 

 woiild lead us to hesitate to adopt the view in question with- 

 out clear experimental proof. 



Thus, it seems difficult to suppose that the undoubted con- 

 nection in some striking cases between the amount of nitro- 

 gen taken up by the plant, and the amount of starch or sugar 

 formed, is to be explained by an assumption which implies 

 that a chief office of the nitrogenous bodies of plants is to 

 serve as intermediate only, in the transformations necessary 

 for the formation of the non-nitrogenous substances. The 

 view does not, however, assume that nitrogen is eliminated 

 from the plant in the process, and so lost. Then, again, 

 plants, such as many of the Leguminosae, which are character- 

 ised by assimilating relatively very large amounts of nitrogen 

 over a given area of land, and by the formation of very large 

 amounts of proteid in proportion to plant surface, produce 

 relatively small amounts of the carbohydrates. 

 An anal- Nor is it irrelevant to refer to the fact that, from theo- 

 ogyfrom retical considerations, it was for many years assumed, espe- 

 world. cially in Germany, in opposition to the teachings of our own 

 numerous direct experiments, that in the animal body the 

 non-nitrogenous substance — fat — was mostly, if not always, 



