SECT. VI. ELABORATION OF OXYGENE. 



only at the expence of their own proper substance ; 

 the interior of the stem, or a portion of the root, or 

 the lower leaves decaying and giving up their ex- 

 tractive juices to the other parts. 



Thus it appears that oxygene gas, or that consti- Conclud- 

 tuent part of the atmospheric air which has been 

 found to be indispensable to the life of animals is 

 also indispensable to the life of vegetables ; on both 

 which accounts it seems to have well merited the 

 appellation of vital air, by which it was at one time 

 designated. But although the presence and action 

 of oxygene is absolutely necessary to the process of 

 vegetation, plants do not thrive so well in an at- 

 mosphere of pure oxygene, as in an atmosphere of 

 pure or common air. This was proved by an ex- 

 periment of Saussure's, who having introduced some 

 plants of Pisum sativum that were but just issuing 

 from the seed into a receiver containing pure 

 oxygene gas, found that in the space of six days 

 they had acquired only half the weight of such as 

 were introduced at the same time into a receiver 

 containing common air. From whence it follows 

 that oxygene, though the principal agent in the 

 process of vegetation is not yet the only agent ne- 

 cessary to the health and growth of the plant, and 

 that the proportion of the constituent parts of the 

 atmospheric air is just what it ought to be, as well 

 for the purposes of vegetable as of animal life ; being 

 at once an indication both of the wisdom and good- 

 ness of Him by whom it was established. 



