THE NATURE OF HUMUS AND ITS RELATION TO 



PLANT LIFE* 



S. L. JODIDI 



{Office of Physiological and Fermentation Investigations, Bureau of Plant 

 Industry, U. S. Department of Agriculture, Washington, D. C.) 



Considerable progress, recently, in connection with our knowl- 

 edge of the chemical nature of "humus" makes it desirable briefly 

 to review the results obtained. 



Up to a few years ago the generally accepted idea was that 

 humus consisted of but a few organic Compounds. This was largely 

 due to the work of a number of investigators, such as BerzeHus/ 

 Detmer,^ Braconnot,^ Malaguti,^ Terreil,^ and especially Mulder^ 

 and his school, who held that humus consists of a few simple organic 

 substances which are chiefly acid in their nature (or at least can be 

 converted into acids by treatment with alkahes), and which are 

 closely related to each other. Thus, according to Mulder, ulmic 

 acid, the first product in the decomposition of organic matter, is 

 gradually converted into humic acid, geic acid, apocrenic and crenic 

 acids, in the order named, all of which consist of but three Clements : 

 carbon, hydrogen, and oxygen. 



This conception of Mulder's and of contemporary writers may 

 have been due, in part, to the facts that protein matters were then 

 assumed to have a uniform" composition; that the known carbohy- 



* Published by permission of the Secretary of Agriculture. Based largely 

 upon the work conducted during the last six years by the writer while he was 

 connected with the Michigan and Iowa Agricultural Experiment Stations. Re- 

 ported to the Biological Division of the American Chemical Society (see p. 89). 



1 Berzelius: Lehrbuch d. Chemie, 3. Aufl., 8 (1839). 



2Detmer: Landw. Versuchsstationen, 14 (1871). 



^Braconnot: Ann. chim. phys., 12, 191 (1819). 



4Malaguti: Ibid. [3] 54. 407 (1858); Ann. (Liebig), 17, 52 (1836). 



^Terreil: Bul. de la soc. chim. [2] 44, 2 (1885). 



6 Mulder: Ann. (Liebig), 36, 243 (1840) ; Chemie der Ackerkrume; Jour. f. 

 pract. ehem., 21, 343 (1840). 



■^ Kossei: Berichte d. d. ehem. Ges., 34, 3245 (1901). 



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