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CHAPTER II. 



OF THE FOOD OF THE VEGETATING PLANT. 



IF the embryo when converted into a plant and Derived 

 fixed in the soil is now capable of abstracting from earth and 

 the earth or atmosphere the nutriment necessary t 

 its growth and developement, the next object of 

 the phytologist's inquiry will be that of ascertaining 

 the substances which it actually abstracts, or the 

 food of the vegetating plant, 



What then are the component principles of the 

 soil and atmosphere ? The investigations and dis- 

 coveries of modern chemists have done much to 

 elucidate this dark and intricate subject. Soil, in 

 general, may be regarded as consisting of earths, 

 water, vegetable mould, decayed animal substances, 

 salts, ores, alkalies, gases, perhaps in a proportion 

 corresponding to the order in which they are now 

 enumerated ; which is at any rate the fact with re- 

 gard to the three first, though their relative propor- 

 tions are by no means uniform. The atmosphere has 

 been also found to consist of at least four species of 

 elastic matter nitrogene, oxygene, carbonic acid 

 gas, and vapour ; together with a multitude of mi- 

 nute particles detached from the solid bodies occu- 

 pying the surface of the earth, and wafted upon 

 the winds. The two former ingredients exist in 



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