208 HOW CROPS GROW. 



Relative Quantities of Carbon, Hydrogen, Oxygen, 

 and Nitrogen, in dry substance, after deducting the some- 

 what variable amount of ash, (per cent). 



TABLE VII. Br. 



5. The Tables V, VI, and VII, demonstrate that while 

 the absolute quantities of the elements of the dry oat 

 plant continually increase to the time of ripening, they do 

 not increase in the same proportion. In other words, the 

 plant requires, so to speak, a change of diet as it advances 

 in growth. They further show that nitrogen and ash are, 

 relatively more abundant in the young than in the mature 

 plant ; in other words, the rate of assimilation of Nitrogen 

 and fixed ingredients falls behind that of Carbon, Hydro- 

 gen, and Oxygen. Still otherwise expressed, the plant as it 

 approaches maturity organizes relatively more amyloids 

 and relatively less albuminoids. 



The relations just indicated appear more plainly when 

 we compare the Quantities of Nitrogen, Hydrogen, and 

 Oxygen, assimilated during each period, calculated upon 

 the amount of Carbon assimilated in the same time and 

 assumed at 100. 



TABLE VIII. Br. 



1st Period, 

 3d " 

 4th " 

 5th " 



From Table VIII we see that the ratio of Hydrogen to 

 Carbon regularly diminishes as the plant matures ; that of 

 Nitrogen falls greatly from the infancy of the plant to the 

 period of full bloom, then strikingly 'increases during the 



