SECT. VI. ELABORATION OF OXYGENE. 105 



The general conclusion to be drawn from these 

 observations is, that the quantity of oxygene con- 

 sumed by the leaves is relative to the situation in 

 which the plant naturally vegetates ; and that plants 

 vegetating in a barren soil, or in a rarefied at- 

 mosphere, or in a marshy situation, consume, in the 

 same circumstances, less oxygene than such as vege- 

 tate in a fertile soil with an abundant supply of 

 atmospheric air. 



But in saying that any quantity of oxygene was 

 consumed, it is not meant that it was all inhaled by 

 the plant ; the greater part of it was often employed 

 in the formation of carbonic acid gas in the at- 

 mosphere of the receiver : for it does not appear 

 that the actual inhalation of oxygene had in any 

 instance perceptibly exceeded the volume of the 

 leaves. It was for the most part less. 



Such then is the detail and rationale of the alternate 

 processes of the inhalation and extrication of oxygene 

 by the leaves of the vegetating plant. Do any of the 

 other parts of the plant perform similar functions? 



If a sound and fresh root deprived of its stem is On the 

 put into a receiver filled with atmospheric air and r 

 placed over mercury, it inhales indeed a small por- 

 tion of oxygene and hence diminishes the volume 

 of its atmosphere, but it consumes, and seems also 

 to inhale a much larger portion ; while the oxygene 

 that thus disappears is employed in the formation of 

 carbonic acid with carbon, which it abstracts from 

 the root. If the root is immediately removed into 



