62 OF CARBON. 



mospbere of the carbon exbaled by all animals, 

 their proper attribute is only assigned to them. 



A soil in which plants vegetate vigorously 

 contains moisture, which is indispensably 

 necessary to their existence. Carbonic acid 

 also is always present in such a soil, whether 

 it has been abstracted from the air, or gene- 

 rated by the decay (as before explained) of 

 vegetable matter, and water also, from what- 

 ever source in nature it is derived, invariably 

 contains carbonic acid gas. 



Plants during their life possess the power 

 of absorbing, by the spongelets of the roots, 

 moisture, and this moisture contains carbonic 

 acid gas, derived from either of the sources 

 above described. Is it therefore surprising 

 that plants should again give off this carbonic 

 acid, when light, the power which enabled the 

 plant to decompose and assimilate this carbon, 

 is absent ? 



Carbonic acid thus absorbed by the roots is 

 dissolved in the sap which pervades all 

 parts of the plant, and evaporates every 

 moment through the leaves with the water, in 

 quantity corresponding to such evaporation. 



*' Neither this emission of carbonic acid nor 

 the absorption of oxygen has any ccmnexion 

 with the process of assimilation. The former 

 is a mechanical, the latter purely a chemical 

 process." If this view of the subject is correct, 

 those plants which require the presence of 

 oxygen to convert their volatile constituents 

 into resins, should absorb the most when the 

 influence of the light is withdrawn, and such 



