46 OF CARBON. 



instanced : however, it is enough for the pur- 

 pose proposed, and it only remains to prove 

 that the purification of such effluvia is the of- 

 fice performed by plants. 



This peculiar property of the vegetable tribe 

 is so easy of demonstration that every one may 

 convince himself of its existence with very lit- 

 tle trouble. 



The leaves and green parts of plants absorb 

 carbonic acid gas, and give off an equal volume 

 of oxygen, and this they do quite indepen- 

 dently of the plant itself. For instance, if the 

 stem of a plant is placed in water containing 

 carbonic acid gas, and in this state exposed to 

 the sun's rays, the carbonic acid is found to 

 have entirely disappeared from the water, and 

 if the experiment has been conducted under a 

 glass receiver filled with w^ater, an equal bulk 

 of oxygen gas will be found to have been 

 emitted, and when no more gas is given off, it 

 is a sign that all the carbonic acid gas is de- 

 composed, but the process immediately recom- 

 mences if a new portion of it is added. 



The experiments of De Saussine farther 

 prove that plants increase in weight during 

 this decomposition, but in a greater proportion 

 than can be accounted for by the assimilation 

 of carbon alone; and hence it is referred that 

 hydrogen, one of the elements of water, is assi- 

 milated at the same time, and thus a new source 

 of oxygen arises to supply the loss the air is 

 constantly suffering. 



This simple experiment incontestably proves 

 that carbon is assimilated by the leaves of 



