It is quite evident that in the case of these gramineous crops, wheat 

 and barley, which contain a comparatively low percentage of nitrogen, 

 and assimilate a comparatively small amount of it over a given area, 

 there was a greatly increased amount of carbon assimilated by the addi- 

 tion of nitrogenous manure alone. In the case of the wheat, there was 

 much more effect from a given amount of nitrogen supplied as nitrate, 

 which was always applied in the spring, than from an equal quantity as 

 ammonium-salts, which were applied in the autumn and the nitrogen of 

 which was subject to winter drainage. There is also more effect from 

 ammonium-salts applied to barley than to wheat ; the application having 

 been made for the former in the spring and for the latter in the autumn. 

 It should be observed that there was this greatly increased assimilation of 

 carbon in the wheat and in the barley for more than twenty years, with- 

 out the addition of any carbon to the soil. It is, indeed, certain that, 

 in the existing condition of our old arable soils, the increased growth 

 of our staple starch-yielding grains is greatly dependent on a supply of 

 nitrogen within the "soil. It'is equally certain that the increased pro- 

 duction of sugar in the gramineous sugar-cane, in the tropics, is likewise 

 greatly dependent on the supply of nitrogen within the soil. 



It will further be of interest to call attention to the connection between 

 nitrogen accumulation, chlorophyl formation, and carbon assimilation. 



TABLE IV. 



Relation of Carbon assimilation to Nitrogen accumulation, and to Chlo- 

 rophyl formed. 



* The figures given in parenthesis are on the substance partially dried, but not fully dried at 100 C. 



It should be observed that the amounts of chlorophyl recorded are 

 as stated, relative, and not actual ; and the figures show the relative 

 amounts for the individual members of each pair of experiments, and not 

 the comparative amounts as between one set of experiments and another. 

 It should further be stated that the chlorophyl determinations were 

 kindly made by Dr. W. J. Russell, F. R. S., of London, in specimens 

 collected at Rothamsted, whilst the wheat and barley were still green, 

 and actively growing. 



It will be seen, in the first place, that the separated leguminous herbage 

 of hay contained a much higher percentage of nitrogen in its dry matter 

 than the separated gramineous herbage ; and that, with the much higher 

 percentage of nitrogen in the leguminous herbage, there was also a much 

 higher proportion of chlorophyl. 



