PROPERTIES OF HUMUS. 33 



acid or humin, according as they were soluble or 

 insoluble in alkalies ; although in their composition 

 and mode of origin, the substances thus confounded 

 might be in no way allied. 



Not the slightest ground exists for the belief that 

 one or other of these artificial products of the de- 

 composition of vegetable matters exists in nature in 

 the form and endowed with the properties of the 

 vegetable constituents of mould; there is not the 

 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 appar- 

 ent reason, imputed the known properties of the 

 humus and humic acids of chemists to that constitu- 

 ent 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 substance 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 

 considered by many as so firmly established, that any 

 new argument in its favor has been deemed unneces- 

 sary; the obvious difference in the growth of plants, 

 according to the known abundance or scarcity of 

 humus in the soil, seemed to afford incontestable 

 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 



* This remark applies more to German than to English botanists and 

 physiologists. In England, the idea that humus, as such, affords nour- 

 ishment to plants is by no means general ; but on the Continent, the 

 views of Berzelius on this subject have been almost universally adopt- 

 ed.— Ed. 



