64 *OOD OF THE VEGETATING PLANT. CHAP. I. 



of water. The volume of its atmosphere was in- 

 deed diminished during the period of its vegetation; 

 but this is to be accounted for by another cause, as 

 will appear in the course of tracing the progress of 

 vegetation.* 

 But foond Our conclusion therefore must be that hydrogene 



to be un- ,, i i 



favourable is unfavourable to vegetation, and does not serve aa 

 tatiot?" the food of plants. But hydrogene is contained 

 in plants as is evident from their analysis ; and if 

 they refuse it when presented to them in a gaseous 

 state, in what state do they then acquire it? To this 

 question it is sufficient for the present to reply, that 

 if plants do not acquire their hydrogene in the state 

 of gas, they may at least acquire it in the state of 

 water, which is indisputably a vegetable food, and 

 of which hydrogene constitutes one of the com- 

 ponent parts. 



SUBSECTION V. 



Carbonic Oxide. When plants were confined 



by Saussure in atmospheres of carbonic oxide, they 



Unfavour- required nearly the same condition to support ve- 



able to ve- . , . .. . 



getation. getation, and exhibited nearly the same pheno- 

 mena as in nitrogene. Such as were deprived of 

 their green parts died in the course of a few days. 

 The vegetation of Peas whose leaves were com- 

 pletely developed was languid in the sun, and did 

 not succeed at all in the shade. The Epilobium 



* Sur la Veg. chap. vi. sect. 4. 



