. COMPOSITION IN SUCCESSIVE STAGES. 203 



Siegert, who has collected these data, ( Vs. St., Ill, 147,) 

 and who experimented on the influence of phosphatic 

 and nitrogenous fertilizers upon the composition of wheat 

 and rye, gives as the general result of his special inquiries, 

 that Phosphoric acid and Nitrogen stand in no constant 

 relation to each other. Nitrogenous manures increase the 

 per cent of nitrogen and diminish that of phosphoric 

 acid. 



Other Relations. All attempts to trace simple and 

 constant relations between other ingredients of plants, 

 viz. : between starch and alkalies, cellulose and silica, etc., 

 etc., have proved fruitless. 



It is much rather demonstrated that the proportions of 

 the constituents is constantly changing from day to day 

 as the relative mass of the individual organs themselves 

 undergoes perpetual variation. 



In adopting the above conclusions, it is not asserted 

 that such genetic relations between phosphates and al- 

 buminoids, or between starch and alkalies, as Liebig first 

 suggested and as various observers have labored to show, 

 do not exist, but simply that they do not appear from 

 the analyses of plants. 



2. 



THE COMPOSITION OF THE PLANT IN SUCCESSIVE 

 STAGES OF GROWTH. 



We have hitherto regarded the composition of the plant 

 mostly in a relative sense, and have instituted no compari- 

 sons between the absolute quantities of its ingredients at 

 different stages of growth. We have obtained a series of 

 isolated views of the entire plant, or of its parts at some 

 certain period of its life, or when placed under certain con- 

 ditions, and have thus sought to ascertain the peculiarities 

 of these periods and to estimate the influence of these con- 



