ASSIMILATION OF ELEMENTS. 51 



the oxide of carbon, will give one volume of the oxide, -f | a volume 

 of oxygen gas. 



Thus, in the hypothesis which we now discuss, for each volume 

 of carbonic acid that is modified by the vegetation, there will be half 

 a volume of oxygen gas disengaged. Any oxygen more than this 

 half volume which appears, must be regarded as proceeding from 

 the decomposition of water, the hydrogen of which will have been 

 assimilated by the plant at the same time as the carbonic oxide de- 

 rived from the carbonic acid ; and this view would perhaps enable 

 us to conceive how the volume of oxygen which is disengaged du- 

 ring the process of vegetation, may exceed the volume which. ought 

 to be produced, if the carbonic acid decomposed really passed into 

 the state of carbonic oxide. 



We may perchance obtain a more convincing proof of the separa- 

 tion of the elements of water, in analyzing plants grown in a soil 

 absolutely without any organic matter capable of affording them hy- 

 drogenous elements. 



In fact, if a plant, which is grown under such circumstances, con- 

 tains hydrogen in any larger proportion than that which were neces- 

 sary to transform its oxygen into water, we might conclude, with 

 some certainty, that the elements of water had been separated ; the 

 objection made on the score of the presence of manure would then 

 be got rid of entirely. The analyses which have already been laid 

 before the reader supply data for this investigation ; it has only to 

 be ascertained whether, in the elements gained in the course of 

 vegetation, the hydrogen is in excess with reference to the oxygen 

 or not. The following table presents a summary view of our ex- 

 periments : 



Oxysren Hydroj^en HyJroo^eii Hydrojren 



assimilated, assimilated, forming' water, in excess. 



Experiment 1. TrefoU 18.926 2.717 2.362 0.355 



Experiment 2. Peas 19.096 3.319 2.392 0.926 



Experiment 3. Wheat 9.386 1.204 1.173 0.030 



Experiment 4. Transplanted Trefoil . • 6.854 1.495 0.849 0.646 



Experiments. Oats 12.410 1.343 1.343 



In the four first experiments, the hydrogen gained evidently ex- 

 ceeds very sensibly the quantity required by the oxygen to form 

 water. The experiment with the oats, indeed, presents an excep- 

 tion ; but it must be remembered that here a loss of azote was ascer- 

 tained. These analyses, therefore, appear to indicate an assimilation 

 of hydrogen in the course of vegetation, in consequence of a decom- 

 position of water analogous to that of carbonic acid, and very proba- 

 bly effected by the same means. 



