38 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 ¢ 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. { 
Much has been written on the humus compounds, particu- 
larly those found in peat. Mulder,§Hoppe-Seyler, || Griese- 
bach, Senft,** Friih,tt have treated more or less of various 
compounds. Friih gives the best general account and the 
following notes are taken from his paper. He 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 131107. 1893. 
+t Hoppe-Seyler. Hoppe-Seyler’s Zeit. f. phys. Chemie 181101. 
~ 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) 86 :343. 
1840. 
|| Hoppe-Seyler. 1. c. 
{ Griesebach. Uber die Bildung des Torfes in den Emsmooren. Gét- 
tingen. 1846. 
** Senft. Die Humus, Marsch und Torfbildungen. Leipzig. 1862, 
tt Fruh, J. J. Uber Torf und Dopplerit. Ziirich. 1883. (Gives long 
bibliography.) 
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