68 



CHANGES OF COMPOSITION 



[chap. 



barley plots in 1905, where a comparison existed 

 between an unmanured plot, a plot receiving a very- 

 large amount of nitrogenous wool waste, and a third 

 plot which had received the same amount of wool waste 

 a year earlier, so that it had been partially exhausted by 

 the previous crop : — 



Table VIII.— Composition of Barley Crop. Rothamsted, 1905. 



Here the heavy manuring has evidently given rise to an 

 excessive proportion of straw, while the grain produced 

 was so light that much of it had to be dressed out and 

 regarded as offal. 



The principles which have been illustrated in the 

 migration of the materials forming the grain of wheat 

 may also be applied to another case — the changes that 

 go on during the later stages of growth and ripening of 

 meadow hay. Although the plants composing the 

 herbage of a meadow are ia the main perennial and 

 not annual like wheat, the process of nutrition and 

 migration are essentially similar; carbohydrates are 

 manufactured from the carbon dioxide in the atmo- 

 sphere ; nitrogen, phosphoric acid, etc., are taken from 

 the ground and elaborated, until the flowering season is 

 reached, when the movement of the previously formed 

 material into the seed becomes the chief action going 

 on. This is accompanied by an increasing change of 

 non-protein nitrogen compounds into proteins, a loss of 

 sugars by respiration, and a conversion of more soluble 



