158 PROCESS OF NUTRITION. CHAP. III. 



tion of oxygene gas, by means of immersing a plant 

 in distilled water during the day, which had been 

 placed under a receiver filled with atmospheric air 

 deprived of its carbonic acid during the night. The 

 general result was the same as in the foregoing ex- 

 periment ; but owing to the constrained and un- 

 natural situation of the plant the process did not go 

 on so rapidly, and the oxygene given out was con- 

 taminated by a considerable quantity of nitrogene. 

 Leaves sa- When the leaves were kept constantly in the 

 withoxy- shade and in a confined atmosphere, without being 

 gene * at all exposed to the light of day, they continued to 

 inhale oxygene slowly till they were saturated ; 

 when they refused to inhale any more. The quantity 

 necessary to their saturation was about l-^ their 

 volume ; and the time necessary to complete the 

 Still con- process from 36 to 4O hours. But still they con- 

 consume tinued to act upon the surrounding oxygene, with 

 which and with' the carbon they contained they 

 formed carbonic acid, consuming about ~ the oxy- 

 gene they consumed by inhalation, but not thus 

 altering the volume of their atmosphere. But 

 when they were again exposed to the sun, they 

 evolved, in the space of seven or eight hours, a much 

 greater quantity of oxygene than when they were 

 confined in the receiver only for one night. Six 

 cubic inches of the Cactus Opuntia which by re- 

 maining 36 successive hours under a receiver in the 

 dark had inhaled 7~ cubic inches, while in the 

 course of one night it inhaled only four ; evolved 



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