PROCESS OF NUTRITION. CHAP. III. 



contaminated, and the grapes did not ripen : hence 

 we may infer, that the elaboration of oxygene is ne- 

 cessary to the maturity of the fruit. 



General From the whole then of the foregoing ex peri* 

 ment, as relative to the action and influence of 

 oxygene on the plant, and the contrary, the follow- 

 ing is the sum of the results. 



The green parts of plants, but especially the 

 leaves, when exposed in atmospheric air to the suc- 

 cessive influence of the light and shade, inhale and 

 evolve alternately a portion of oxygene gas mixed 

 with carbonic acid. But the oygene is not imme- 

 diately assimilated to the vegetable substance ; it is 

 first converted into carbonic acid by means of com- 

 bining with the carbon of the plant, which withers 

 if this process is prevented by the application of 

 lime or potass. The leaves of aquatics, succulent 

 plants, and ever-greens consume, in equal circum- 

 stances, less oxygene than the leaves of other plants. 



The roots, wood, and petals, and in short all parts 

 not green, with the exception of some coloured 

 leaves, do not effect the successive arid alternate in- 

 halation and extrication of oxygene ; they inhale it 

 indeed, though they do not again give it out, or as- 

 similate it immediately, but convey it under the 

 form of carbonic acid to the leaves, where it is 

 decomposed. 



Oxygene is indeed assimilated to the plant, but 

 not directly, and only by means of the decomposi- 

 tion of carbonic acid ; when part of it, though in a 



