82 CHYMISTRY APPLIED TO AGRICULTURE. 



entrance of the gallery. A comparative analysis of these 

 various portions afforded me, from those which grew at the 

 bottom of the gallery, only water saturated vvith carbonic 

 acid, a small quantity of mucilage, and a little parenchy- 

 mous fibre swimming in the liquid. The proportion of 

 acid was much less, and that of ligneous fibre more con- 

 siderable, in the mushrooms plucked from the middle and 

 entrance of the gallery, particularly in the last. Those 

 from the dark part of the gallery contained only the ele- 

 ments of nutrition not elaborated ; whilst in the other, the 

 process of assimilation was carried on more or less per- 

 fectly, in proportion as light and atmospheric air had 

 access to them to facilitate vegetation ; otherwise, as car- 

 bonic acid was most abundant in those plants which grew 

 in darkness, their texture ought to have been the most 

 thoroughly impregnated with it. 



ARTICLE II. 



The Influence of Oxygen Gas upon Nutrition. 



Healthy leaves absorb oxygen gas during the night, but 

 the phenomena which they present vary according to the 

 nature of the plant. Those of the oak, the horse-chestnut, 

 the false acacia, Slc, absorb oxygen and evolve a less 

 volume of carbonic acid than they consume of oxygen. 

 The leaves of fleshy plants diminish the volume of air by 

 absorbing from it oxygen, without which they sensibly 

 give out carbonic acid. 



The quantity of oxygen absorbed by plants is in propor- 

 tion to their state of vigor. It is likewise regulated by 

 temperature ; being greater at 88° than at 55° or at 66° 

 Fahrenheit. 



When plants remain several nights under receivers filled 

 with atmospheric air, the leaves continue, though slowly, 

 to absorb oxygen, with which they are saturated as soon 

 as they contain 1;^ their volume. When the leaves are 

 saturated with oxygen they begin to form carbonic acid, 

 by combining their carbon with the oxygen of the atmo- 

 sphere, without at the same time changing its volume, as 

 they never employ, for the formation of this acid, all the 



