DECOMPOSITION OF NON-NITROGENOUS ORGANIC MATTER 



429 



2. Hemicelluloses, or the condensation products of hexoses (galactose, man- 

 nose) and of pentoses (arabinose, xylose), readily hydrolyzed by dilute mineral 

 acids. 



3. Pectins, different in composition, but related to the hemicelluloses. 7 



4. Lignins, forming complex physical, absorption compounds or mechan- 

 ical incrustations with celluloses, known as ligno-celluloses, which constitute 

 the woody tissues of plants. 8 



5. Corky or cutinized lamellae, identified microscopically by the Sudan- 

 glycerol reaction and not well defined chemically. 



The woody parts of plants or the plant cell membranes are usually- 

 referred to as "crude fiber." This is made up of cell walls composed 

 principally of celluloses; they are accompanied by various other sub- 

 stances, depending upon the nature of the plant; even the carbon con- 

 tent of celluloses of different origin varies. 9 This is probably due, not 

 to differences in the constitution of the celluloses, but to the differences 



TABLE 34 

 Mineral composition of a few plant products' 



Corn stover. 

 Corn cobs . . 

 Oat straw . . , 

 Wheat straw 

 Clover hay . . 

 Timothy hay 



N 



0.81 

 0.50 

 0.58 

 0.53 

 2.17 

 0.84 



0.07 

 0.03 

 0.09 

 0.09 

 0.18 

 0.13 



K 



0.78 

 0.64 

 1.09 

 0.83 

 1.12 

 1.34 



in the amount and kind of impurities present. In the case of cotton, 

 flax and hemp, pectin forms the chief impurity. In the case of straw, 

 wood and jute, lignin is the impurity. This gave rise to the terms 

 pecto-celluloses and lignocelluloses. Celluloses of different origin are 

 decomposed with different rapidity, 10 probably as a result of differ- 

 ences in the physical condition as well as impurities present. 



6 Thorne, C. E. Farm manures. O. Judd. New York. 1914. 



7 Ehrlich, F. Die Pektinstoffe, ihre Konstitution und Bedeutung. Chem. 

 Ztg., 41: 197-200. 1917. 



8 Riefenstahl, R. Der gegenwartige Stand der Ligninchemie. Ztschr. 

 angew. Chem., 37: 169-177. 1924. 



9 Konig, J. Bestimmung der Cellulose, des Lignins und Rutins in der Roh- 

 faser. Z. Unters. Nahrungs u. Genussm., 12: 388. 1906; Ber. deut. chem. 

 Gesell., 39: 3564-3570. 1906. 



10 Ernest, A. Beitrag zur Kenntnis einiger Cellulosen. Ber. deut. chem. 

 Gesell., 39: 1947-1951. 1906. 



