PROPERTIES OF HUMUS. / 



shadow of a proof that one of them exerts any influ- 

 ence on the growth of plants either in the way of 

 nourishment or otherwise. 



Vegetable physiologists have, without any appa- 

 rent reason, imputed the known properties of the 

 humus and humic acids of chemists to that consti- 

 tuent of mould which has received the same name, 

 and in this way have been led to their theoretical 

 notions respecting the functions of the latter sub- 

 stance in vegetation. 



The opinion that the substance called humus is 

 extracted from the soil by the roots of plants, and 

 that the carbon entering into its composition serves 

 in some form or other to nourish their tissues, is so 

 general and so firmly established, that hitherto any 

 new argument in its favour has been considered 

 unnecessary ; the obvious difference in the growth 

 of plants according to the known abundance or 

 scarcity of humus in the soil, seemed to afford in- 

 contestable proof of its correctness. 



Yet, this position, when submitted to a strict ex- 

 amination, is found to be untenable, and it becomes 

 evident from most conclusive proofs that humus in 

 the form in which it exists in the soil does not yield 

 the smallest nourishment to plants. 



The adherence to the above incorrect opinion 

 has hitherto rendered it impossible for the true 

 theory of the nutritive process in vegetables to 

 become known, and has thus deprived us of our 

 best guide to a rational practice in agriculture. 



