1908,] PUBLIC DOCUMENT — No. 33. 69 



D. The Pentosans. 



J. B. hINDSEY. 



(a) Character of Plant Tissue. 



Various investigations have shown that the larger part of 

 the cellular structure of vegetables and coarse fodders con- 

 sists : ^ (1) of substances insoluble in water, but soluble in 

 dilute mineral acids, and which are classified as hemi-ccllu- 

 loses ; (2) of sul)stances insoluble to any extent in dilute 

 mineral acids, alkali, or F. Schulze's reagent, and which are 

 turned blue by sulphuric acid and iodine, namely, the true 

 celluloses ; (3) of lignin acids, which compose one-third to 

 one-half of the true woods, but exist only in small quan- 

 tities, if at all, in the soft new cells of young plants and 

 vegetables. 



Under the hemi-celluloses^ belong the mother substances 

 dextran, lawulan, mannan, galactan and pentosans (araban 

 and xylan), which on inversion yield dextrose, Isevulose, 

 mannose, glactose, arabinose and xylose. These hemi-cel- 

 Inloses are intermixed and perhaps chemically united to the 

 true celluloses and limio-celluloses in the cell walls of 

 plants and seeds. In some cases they have been recognized 

 as reserve material, and are used as food in the sprouting 

 of the seed. 



The true celluloses, upon being dissolved in strong sul- 

 phuric acid, and the resulting product hydrolyzed with dilute 

 acid, yield dextrose as a rule, hence the name dextroso cel- 

 lulose. Schulze has also recognized mannose and xylose, 

 consequently there exist dextroso, mannoso and pentose 

 celluloses. 



^ This classification does not include amyloid, a substance soluble in water, 

 and yielding various sugars by hydrolysis. See Winterstein, Zeitsch. f. physiol. 

 Chem., 15, 1892; also Agricultural Science, 1893, p. 162. 



^ See various publications of E. Schulze in Zeitsch. f. physiol. Chem. 



