12 RESULTS OF EXPERIMENTS AT ROTHAMSTED, 



It is natural to ask what is the explanation of the apparently 

 anomalous result, that the crops which are characterised by containing 

 comparatively little nitrogen, and by yielding large amounts of non- 

 nitrogenous products starch, sugar, and cellulose are especially 

 benefited by the application of nitrogenous manures ; and that, under 

 their influence, they yield greatly increased amounts of those non- 

 nitrogenous bodies ? 



It is, perhaps, little more than stating the facts in another way to 

 say, as is the case, that the luxuriance, or activity of growth, of all 

 these crops, is very greatly enhanced by nitrogenous manures ; and 

 that, since their .special products are these non-nitrogenous substances, 

 the natural result of the increased luxuriance is to increase the 

 formation of the bodies which are their essential or characteristic 

 products. 



A further possible explanation of the curious results has, however, 

 been suggested.* 



Thus, on purely chemical and physiological grounds, and, so far as 

 would appear, without any special reference to the fact that, in the case 

 of 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 sulphur 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 formation 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 inconsistent 

 with the conditions which we have seen to be favourable 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, require more evidence than is at present available, to 

 establish such a conclusion ; whilst there are considerations which would 

 lead us to hesitate to adopt the view in question, without clear 

 experimental proof. 



Thus, it seems difficult to suppose, that the undoubted connection 

 in some striking cases, between the amount of nitrogen 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 



* See Vines' Lectures on the " Physiology of Plants," p. 140, et seq. 



