OF THE INORGANIC CONSTITUENTS OF PLANTS. 105 



than this, that it is the ammonia of the atmosphere 

 which furnishes nitrogen to plants.* 



Carbonic acid, water, and ammonia, contain the 

 elements necessary for the suj^port of animals and 

 vegetables. The same substances are the ultimate 

 products of the chemical processes of decay and pu- 

 trefaction. All the innumerable products of vitality 

 resume, after death, the original form from which 

 they sprung. And thus death, ^ — the complete dis- 

 solution of an existing generation, — becomes the 

 source of life for a new one. 



CHAPTER VI. 



OF THE INORGANIC CONSTITUENTS OF PLANTS. 



Carbonic acid, water, and ammonia, are necessary 

 for the existence of plants, because they contain the 

 elements from which their organs are formed; but 

 other substances are likewise requisite for the for- 

 mation of certain organs destined for special func- 

 tions peculiar to each family of plants. Plants ob- 

 tain these substances from inorganic nature. In the 

 ashes left after the incineration of plants, the same 

 substances are found, although in a changed con- 

 dition. 



Although the vital principle exercises a great pow- 

 er over chemical forces, yet it does so only by direct- 

 ing the way in which they are to act, and not by 

 changing the laws to which they are subject. Hence 

 when the chemical forces are employed in the pro- 

 cesses of vegetable nutrition, they must produce the 

 same results which are observed in ordinary chemical 

 phenomena. The inorganic matter contained in plants 



* From some experiments with respect to the action of light upon 

 plants, Dr. Daubeny is inclined to suspect that in some cases hydro- 

 gen is assimilated whilst nitrogen is disengaged. See his Memoir in 

 Fhilos. Trans, 1836. 



