COMPOSITION IN SUCCESSIVE STAGES. | 203 
Siegert, who has collected these data, ( Vs. S¢., II, 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. 
vA 
§ 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- 
