85 
cases (310.) where we have seen it to be afforded by 
plants in confined. air. 
320. The gases, which thus enter by the roots and 
exist in the sap, will be conveyed with it to the 
leaves. M. Senebier plunged branches of the peach 
tree into recipients containing water charged with 
carbonic acid ; so that, in some instances, the ligneous 
extremity of the branch was also immersed, while, 
in other instances, this extremity was confined in an 
empty bottle. The result was, that the leaves of the 
branches, whose ends were immersed, afforded in 
sunshine double the quantity of oxygen that was 
yielded by the others ; whence he concludes, that 
the carbonic acid passes with the water into the leaves 
and is then decomposed *. In the experiments of M. 
de Saussure, the attraction of oxygen by water, the 
absorption of this water by the roots, and the subse- 
quent expulsion of oxygen from the leaves, are clear- 
ly established f ; so that the conveyance of gas ous 
fluids into the leaves, by this route, cannot be rea- 
sonably doubted. 
321. But not only by the roots does carbonic acid 
thus obtain admission into vegetables, but likewise 
by the leaves. The power of the leaves to absorb 
water has been amply established by the experiments 
of Bonnet ; and the gaseous fluids, which exist in 
this water, may readily be conceived to enter with 
it. The production of oxygen gas by leaves, im- 
rnersed in water containing carbonic acid (288.), can* 
* Physiol. Veg. torn. iii. p. 2'25. 
| Rcdgprches, p, 111, 
