oO 



which reciprocal action can in no way be accounted 

 for, but by that conversion of the one gas into the o- 

 ther, which is here supposed actually to have place. 



39. To effect this conversion, however, of the 

 oxygen gas, carbon must be from some source sup- 

 plied. This Dr Woodhouse supposes, as in the 

 case of seeds, to proceed either from the organized 

 remains of the soil in which the plants grow, or from 

 the carbon of the decayed leaves, when confined a 

 considerable time in a given bulk of air * : but it 

 has been shewn, that carbonic acid is equally pro- 

 duced (31.), where there is no soil present to af- 

 ford carbon ; and that it appears also in a few 

 hours (31.), and before the leaves, therefore, exhi- 

 bit any si^n of decay. Indeed, there does not ap- 

 pear any good reason why oxygen gas should be so 

 essential to the life of vegetables, if it could be act- 

 ed on or changed by those parts of them only which 

 are already dead. To the living plant, therefore, as 

 well as to the seed (20.), \ve must look as affording 

 carbon, and by the union of this carbon with the 

 oxygen gas of the air, must we consider the car- 

 bonic acid met with in vegetation to be formed. 



40. But as this carbonic acid is produced in ve- 

 lion, the oxygen gas proportionally disappears, 



(3O. ct seq.), and when this substitution is com- 

 plete, the plant gradually declines and dies. To what 

 cause is this effect to be immediately ascribed ? It 

 must arise from the superabundance either of ni- 

 trogen gas, or of carbonic acid, or from the defi- 



Nicbolson's Journal, July 1802, p. 



