ON THE FOOD OF PLANTS. 135 



ingredient in the food of plants, and that by its 

 gravity it will penetrate into the soil, no method 

 more favorable for its generation and equal dis- 

 tribution can be devised, than by my mode of 

 application j and if carburetted hydrogen be 

 either an unwholesome food, or by its rapid 

 escape, the occasion of a great waste of carbon ; 

 and nitrogene gas be poisonous, or obnoxious, 

 when in contact with the food; no mode can 

 be more favorable to, or productive of, both 

 those effects, than burying the dung in an un- 

 fermented state. 



If we were to suppose, that a difference in the 

 quality of the food supplied to plants, produced no 

 difference in its effects ; or that the roots possessed 

 the power of selecting the exact quantity and pro- 

 portion of each principle, required for its parti- 

 cular purpose, from any composition that may be 

 presented to it ; we should be driven far off from 

 accounting for the diseases of plants, or for the dif- 

 ference in the size, substance, state, and condi- 

 tion of plants of the same species, when growing 

 in the same situations : and, although we are 

 justified in believing, that a plant having taken 

 in its food in a compound state, possesses the 

 power of dividing and appropriating the different 

 parts to its different purposes, it must be pb- 

 vious, that any unnatural obstruction to the due 



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