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component parts ; of the relation which these latter" 

 bear to, and the influence they exercise upon, the 

 whole organism. We have to acquaint ourselves 

 with the different elements of which plants consist, 

 and to enquire whence they are derived and how 

 they are assimilated. 



If we subject a plant, or^a portion of it, to the 

 process of combustion, we reduce its component 

 parts to their elementary form ; we call those 

 which are combustible the organic, and those which 

 are incombustible the inorganic parts of the plant. 



The organic parts are chiefly derived from the 

 atmosphere ; they consist of four elements 

 Carbon, Hydrogen, 



Nitrogen, Oxygen, 



and are assimilated through the leaves and the roots 

 in the form of Carbonic Acid, Water, and Ammonia. 

 The inorganic parts the ashes of the plant are 

 all derived from the soil, and the most important 

 elements we find in them are 



Potash, Phosphoric Acid, 



Soda, Silicic Acid, 



Lime, Sulphuric Acid, 



Magnesia, Chlorine. 



The inorganic parts are assimilated by the under- 

 ground part of the plant the root. 



All these organic and inorganic elements consti- 

 tute what we call the food of plants : every plant 

 requires thein in- an available form for -its develop- 



