PROCESS OF NUTRITION. CHAP. W. 



gene gas. It may be observed, however, tbat tbe 

 green colour is not an absolutely essential character 

 of the parts decomposing carbonic acid ; because 

 the leaves of a peculiar variety of the d triplex 

 hortensis, in which all the green parts change to 

 red, do still exhale oxygene gas. But all leaves 

 have not the same facility in decomposing carbonic 

 acid; a plant tf Ly thrum Salicaria has been known 

 to decompose in one day seven or eight times its 

 volume, while many other plants cannot decon> 

 pose the one-fifth or even the one-tenth of that 

 quantity; though in general it may be observed 

 that the leaves and other green parts of the plant 

 decompose it in proportion to their surface, and not 

 in proportion to their volume. But how is the 

 formation of nitrogene to be accounted for, which 

 is always found to be extricated along with the 

 oxygene thus evolved by the leaves ? The subject 

 is yet enveloped in much obscurity, as well as the 

 means of giving it the elucidation to be desired ; 

 but perhaps it is abstracted from the interior of the 

 leaf through the medium of the evolved oxygene 

 for which it is known to have an affinity. 



