120 LECTURE VII. 



general results are that when the proportion of oxygen present 

 is large, that of carbon dioxide is small, and vice versa, the 

 proportion of carbon dioxide being smallest in the winter. 

 In most cases the proportion of nitrogen present was approxi- 

 mately that in which it occurs in atmospheric air, though in 

 some instances it appeared that it was the only gas present ; 

 but these observations require confirmation. 



We have now concluded the consideration of the absorp- 

 tion and distribution of the various substances which are 

 absorbed by plants, and we will proceed, in the next lecture, 

 to study their relation to the metabolic processes. 



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