MISSOURI BOTANICAL GARDEN. 



possible in the majority of cases. Our present knowledge 

 of the humus compounds is at best a meager one. They 

 are generally described * as black bodies, which form in the 

 decay of organic substances, and which occur in soil, peat, 

 etc. They are divided f into three groups (according to 

 their solubilities): 1. Such as are soluble in alcohol and 

 dilute alkalies. 2. Such as are very soluble in alkalies and 

 precipitated by acids as gelatinous bodies insoluble in 

 alcohol. 3. Such as are very soluble in alkalies, precipi- 

 tated by acids, the precipitate soluble in alcohol. The 

 substance found in the cypress wood belongs evidently to 

 the second class, one to which a large number of products 

 belong, particularly those obtained from peat and decaying 

 vegetable substances. J 



Much has been written on the humus compounds, particu- 

 larly those found in peat. Mulder, Hoppe-Seyler, ||Griese- 

 bach,H Senft,** Friih,t t have treated more or less of various 

 compounds. Friih gives the best general account and the 

 following notes are taken from his paper. Me says (p. 

 63) : Ulmates and humates, ulmin and humin, ulmic and 

 humic acids in homogeneous masses or in fine particles give 

 a mass which when moist is slightly elastic. In drying 

 these substances contract, become black, shining like glass, 

 hard, and break, with conchoidal fracture. The splinters 



* Beilstein, F. Handbuch der organischen Chemie 1 :1107. 1893. 



f Hoppe-Seyler. Hoppe-Seyler's Zeit. f. phys. Chemie 13 : 1101. 



J Some of the humus compound was sent Dr. Friih who says of it : 

 " It seems to agree in its properties with ulmic acid, or a calcium salt 

 of the same." Dr. Van Bemmelen of Leiden has kindly undertaken to 

 make a more detailed examination. 



Mulder, Liebig's Annalen der Chemie (u. Pharmacie) 36 : 343. 

 1840. 



|| Hoppe-Seyler. 1. c. 



1 Griesebach. Uber die Bildung des Torf es in den Emsmooren. Got- 

 tingen. 1846. 



** Senft. Die Humus, Marsch und Torfbildungen. Leipzig. 1862. 



ft Friih, J. J. Uber Torf und Dopplerit. Zurich. 1883. (Gives long 

 bibliography.) 



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