SECT. VI. ELABORATION OF OXYGENE. 



during the succeeding day, when exposed to the 

 light of the sun, 74- cubic inches also. 



The quantity of oxygene, therefore, which isTh 



,7 . ' tides aiter- 



exhaled during the day is proportional and nearly nately in- 

 equal to the quantity inhaled during the night, or 



during the time of the plant's confinement in the 

 shade up to its saturation. The former quantity is 

 generally indeed somewhat more than the latter, 

 which Saussure regards as being probably owing 

 to the decomposition of water in the plant. But 

 whatever may be the true explication of this par- 

 ticular phenomenon, it is evident that no permanent 

 assimilation of oxygene js effected in the alternate 

 process of its inhalation and extrication by the 

 leaves, so as to increase materially the quantity of 

 dried vegetable substance. 



But as plants vegetating in the shade and in con- Saturation 



occurs 



nned atmospheres become so soon saturated with only in 

 oxygene and refuse to absorb more, one might be ^ ? 

 apt to conclude that plants vegetating even in the $i>her "" 

 open air, if situated in the shade, must become 

 saturated with it also, and refuse to absorb more 

 when placed in an Artificial atmosphere. This, 

 bowever, is not the fact. Saussure tried the ex- 

 periment repeatedly, and found that plants confined 

 in an artificial atmosphere, after having been ex- 

 posed to the open air in the shade, always inhaled 

 oxygene as in other cases ; so that by frequently 

 changing their exposure from the natural to the artifi- 

 cial atmosphere and the contrary, they were capable 



