232 HOW CROPS GROW. 



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 per cent) was found in the ripe leaves; 

 the smallest (0.78 per cent) 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 sev- 

 eral periods of growth. These absolute quantities, 

 as found by Arendt, in a given number of carefully- 

 selected and vigorous plants, do not accord with those 

 obtained by Bretschneider 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 vegeta- 

 tion to develop 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 situated in the best 

 possible conditions, and attaining a uniformly high 

 development. We shall not attempt to compare the two 

 sets of observations, since, strictly speaking, in most 

 points they do not admit of comparison. 



From a knowledge of the absolute quantities of the 

 substances contained in the plant at the ends of the several 

 periods, we may at once estimate the rate of growth, i. e., 

 the rapidity idth 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 periods, and (by subtracting .the first from the 

 second, the second from the third, etc.) the gain from 

 matters absorbed or produced during each period, will 

 serve to justify the deductions that follow, which are 

 taken from the treatise of Arendt, and which apply, of 

 course, only to the plants examined by this investigator. 



