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fertilizing material before our very doors ; it justifies 

 us as little in wasting the phosphoric acid contained 

 in animal refuse, as the existence of coal does in 

 destroying our forests. 



It has been thought very necessary by Government 

 to have a conservancy department for the vegetable 

 world ; then why should we not also have one for the 

 animal world ? Conservancy in the animal kingdom, 

 to which we ourselves belong, is quite as essential 

 indeed, more so than in the vegetable kingdom. 



The importance of drawing especial attention to 

 phosphoric acid will be acknowledged from the 

 foregoing, but it occupies no such particularly 

 prominent place if the general necessities of the 

 plant are only regarded ; for each constituent of 

 plant-food is equally indispensable to the existence 

 and development of plants. 



Under the several heads of the inorganic sub- 

 stances of plant-food, I have essayed to give an 

 idea of the manner in which they are assimilated 

 and absorbed by the vegetable system. It has been 

 mentioned that all the mineral or inorganic sub- 

 stances which enter into the system of plants, do 

 so in a state of solution in water. Only those parts 

 of the soil which are either capable by themselves 

 of being dissolved in water, or may become so by 

 the agency of- certain solvents, as carbonic acid, the 

 alkalis, &c., can be assimilated and utilized as food 

 by plants ; and it is impossible that any particle of 

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