660 The Sources of the Nitrogen of our Leguminous Grojys. 
nitrogenous manures. The estimated increased production of 
total carbohydrates, under the influence of the nitrogenous 
manures, is then given ; and lastly, the estimated gain of carbo- 
hydrates for 1 lb. of nitrogen supplied in manure. Such estimates 
can obviously be only approximations to the truth ; but accepted 
as such, they are of interest and of use, as conveying some 
definite impression of the influence of nitrogenous manures on 
carbon-assimilation, and on carbohydrate-formation.^ 
It is seen that, independently of the underground growth, 
the wheat was estimated to assimilate 988 lb. of carbon per acre 
per annum, under the influence of a complex mineral manure 
alone ; and that the amount was increased to 1 ,590 lb. by the 
addition of 43 lb. of nitrogen as ammonium-salts, to 2,222 lb. 
by 86 lb. of nitrogen as ammonium-salts, and to 2,500 lb. by 
86 lb. of nitrogen as sodium -niti-ate. Accordingly, as shown in 
the second column, the increased assimilation of carbon was, by 
43 lb. of nitrogen as ammonium-salts G02 lb., by 86 lb. as 
ammonium-salts 1,234 lb., and by 86 lb. as sodium-nitrate 
1,512 lb. 
Reckoned in the same way, the increased assimilation of 
carbon in the barley was, for 43 lb. of nitrogen as ammonium- 
salts, 950 lb. per acre ; that is, one-and-a-half time as much as 
by the same application in the case of wheat. 
In the sugar-beet the increased assimilation of carbon, and 
accumulation of it in the roots, was 1,477 lb. per acre by the 
application of 86 lb. of nitrogen as ammonium-salts, and 1 ,908 lb. 
by 86 lb. of nitrogen as sodium- nitrate. There was, therefore, 
more increased assimilation of carbon and accumulation of it in 
the roots of the sugar-beet, than in the grain and the straw of 
wheat, by the same applications of nitrogenous manure. 
In the mangel-wurzel the increased accumulation of carbon 
in the roots was 1,130 lb. by 86 lb. of nitrogen as ammonium-salts, 
and 1,370 lb. by 86 lb. as nitrate ; that is, less than in tliQ removed 
crops (corn and straw) of wheat, and considerably less than in 
the removed crops (the roots) of sugar-beet. 
In the potatoes, reckoned on the increased production of 
tubers only (the tops being left on the land), the increased yield 
of carbon by 86 lb. of nitrogen as ammonium-salts was 762 lb. 
' Tlie morle of calculatinci: the amounts of carbon and of carbohydrates is 
as follows : — From tlic amount of dry substance in the crops the amounts of 
mineral matter and of nitrogenous substance arc deducted, and tlie remainder 
represents approximately the amount of carbohydrates. The amount of car- 
bon in the nitrogenous substance is calculated; and then that in the carbo- 
hydrates, on the assum])tion that, in the wheat, barley, and beans, starch and 
cellulose are the main products ; in the sugar-beet and mangel-wurzel, cane- 
sugar, pectine, and cellulose ; and in the potatoes, starch and cellulose. 
