Researches on Vegetation. 309 



half thai which fonncd tlie carbonic acid ; that the comple- 

 ment of the voh.ime is owing to the azotic gas which is ex- 

 haled from the plant. 



When the carbonic acid, then, is decomposed, its carbon 

 and a half of its oxvgen enter into the composition of. the 

 plant, from which there is exhaled a variable quantify of 

 azotic gas. 



Saussure, indeed, has confirmed that plants which had 

 operated a decomposition of carbonic acid give more carbon 

 than before that decomposition ; those, on the other hand, 

 which are made to vegetate in distilled water and an atmo- 

 sphere deprived of carbonic acid, make no acquisition of 

 carbon. 



It was experiments, probably, made under this circum- 

 stance which gave reason to conclude that plants which ve- 

 getate in pure water and in the open air contain no carbon 

 but that found in the seeds from which tTiey were produced. 

 But Saussure has ascertained, by repeated experiments, that 

 plants exposed to the open air acquire pure carbon by the 

 decomposition of the carbonic acid naturally found in them. 



It had been observed that vegetation produced under dif- 

 ferent circumstances a dilatation or contraction of the at- 

 mosphere in which it is eflected. Saussure shows that the 

 leaves absorb oxygen gas in darkness, and that they emit 

 an equal quantity when exposed to the light; so that the 

 same atmosphere deprived of carbonic acid is, according to 

 common language, corrupted in the night and purified 

 during the day. He denotes this alternate phienomcnon 

 by the words inspiration and expiration, and establishes the 

 relation of these vegetable functions according to the kind 

 of plants and according to the circumstances under which 

 they exist. 



The oxygen gas winch has been inspired is changed into 

 carbonic acid ; the latter its decomposed in the act of ex- 

 piration, and abandons the half of its oxygen, which resumes 

 the clastic state. 



The roots, wood, and petals, perform no inspiration ; 

 but they give up carbon to the oxygen gas which sur- 

 rounds them, and at the same time there is a production 

 of water : green fruits, however, and the voung bark which 

 is still green, enjoy inspiration, and produce a compound 

 effect on the atmospheric air. 



Having exauiined the relation between the living vegeta- 

 ble and the atmosphere, water and the carbonic acid, Saus- 

 sure submits to the same examination vegetable substances 

 deprived of life, 



U 3 Extracts 



