PROPERTIES OF HUMUS. 



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 decomposition 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 influence on 

 the growth of plants, either in the way of nourishment or other- 

 wise. 



Vegetable physiologists have, without any apparent reason, im- 

 puted the known properties of the humus and humic acids of che- 

 mists to that constituent 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 to nourish their tissues, without previously 

 assuming another form, is considered by many as so firmly estab- 

 lished that any evidence 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 examination, is 

 found to be untenable, and it becomes evident from most con- 

 clusive 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 ren- 

 dered it impossible to ascertain the true theory of the nutritive 

 process in vegetables, and has thus deprived us of our best guide 

 to a rational practice in agriculture. Any great improvement 

 in that most important of all arts is inconceivable, without a 

 deeper and more perfect acquaintance with the substances which 

 nourish plants, aod with the sources whence they are derived ; 

 and no other cause can be discovered to account for the fluctuat- 



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

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

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

 of Berzelius on this subject have been almost universally adopted. — Ed. 



