COMPOSITION IN SUCCESSIVE STAGES. 218 
by Arendt that of the stem the upper portion was richest in 
ash throughout the whole period of growth. Of the leaves, 
on the contrary, the lower contained most fixed matters. 
In the ear there occurred a continual decrease from its 
first appearance to its maturity, while in the stem and 
leaves there was, in general, a progressive increase towards 
the time of ripening. The greatest percentage, (10. 5° lo) 
was found in the ripe leaves; the smallest, (0.78°|,,) in the 
ripe lower straw. 
Far more interesting and instructive than the relative 
proportions are 
B—The absolute quantities of the ingredients found 
in the plant at the conclusion of the several periods of 
growth.—These absolute quantities, as found by Arendt, 
in a given number of carefully selected and vigorous 
plants, ds not accord with those obtained by Bretschnei- 
der from) a given area of ground, nor could it be expected 
that they should, because it is next to impossible to cause 
the same amount of vegetation to develope on a number 
of distinct plots. 
Though the results of Bretschneider more nearly rep- 
resent the crop as obtained in farming, those of Arendt give 
a truer idea of the plant when sitnated 9 in the best possible 
conditions, and attaining a uniformly high development. 
We shall not attempt to compare the two sets of observa 
tions, since, strictly speaking, in most points they do not 
admit of comparison. 
From a knowledge of the absolute quantities of the gub- 
stances contained in the plant at the ends of several periods, 
we may at once estimate the rate of growth, 7. ¢., the rapid- 
it, with which the constituents of the plant are either taken 
up or organized. 
The accompanying table, which gives in alternate col- 
umns the total weights of 1,000 plants at the end of the 
several perinls, and, (by subtracting the first from the 
