180 PROCESS OF NUTRITION. CHAP. III. 



that was replaced by an equal quantity of nitrogenc, 

 it goes for nothing in the weight of the plants. 



Before the experiment they weighed in their 

 green state 168*- grains, which were ascertained to be 

 equal to 5 1 grains of dried vegetable matter ; but 

 after the experiment the quantity of dried vegetable 

 matter was equal to 6l grains. There was conse- 

 quently an augmentation of weight of 10 grains, of 

 which 4'2 only can be attributed to the formation of 

 Who in- carbon ; hence it follows most evidently, that there 

 thedecom- na ^ been a decomposition of the water, and an assi- 

 ofm ilation f ' ts component parts, by means of which 

 5*8 grains were added to the weight of the plant. 



The decomposition then, and fixation of water by 

 the vegetating plant is thus, according to Saussure, 

 legitimately inferred ; but it does not appear that 

 plants do in any case decompose water directly 

 that is, by appropriating its hydrogen e and at the 

 same time disengaging its oxygene in the form of 

 gas, which is extricated only by the decomposition 

 of carbonic acid. Plants vegetating in nitrogene 

 gas and exposed to the alternate influence of night 

 and day, do, indeed, extricate a quantity of oxygene 

 equal to many times their volume; but this is be- 

 cause being deprived of the contact of that gas in 

 the first period of experiment, they form of their 

 own substance a supply of carbonic acid gas, which 

 they afterwards decompose : and hence the origin 

 of the oxygene found in their atmosphere. They 



