MANNOSANES 137 



All these compounds have the same formula, 6(C 6 H 10 O 5 + 

 H 2 O), and possess the same characteristics ; they are laevo- 

 rotatory, yield fructose on -hydrolysis, and are fairly soluble 

 in cold water. The majority are difficult to crystallize, and 

 their solutions yield a gum-like substance on evaporation. It 

 is possible that some, at any rate, of these substances may 

 bear the same relation to inulin as dextrin does to starch. 



MANNOSANES. 

 MANNANE. 



The seeds of many plants contain reserve carbohydrate 

 which is generally referred to as reserve cellulose, hemi-cellulose, 

 or para-galactane substances. These materials are often indis- 

 tinguishable from true cellulose by the microchemical means 

 at our disposal. They may, however, be distinguished by the 

 products of their hydrolysis ; thus they form glucose, together 

 with other substances, on treatment with hot dilute hydrochloric 

 or sulphuric acid, whereas ordinary cellulose does not. Also 

 they are dissolved by dilute alkalis, and by cuprammonia after 

 a brief treatment with hot dilute hydrochloric acid. These 

 reserve celluloses contain mannanes and galactanes. 



Mannane serves in the same way as starch as a reserve food- 

 supply to a very large number of different plants. It may be 

 regarded as an anhydride of mannose, since it yields this 

 substance on hydrolysis ; it occurs either alone or united to 

 anhydrides of other sugars, such as glucose, galactose, pentose, 

 etc., in a great many different forms. 



A fairly pure specimen of mannane can be obtained from 

 yeast by a somewhat elaborate method devised by Hessenland.* 

 It is a white amorphous substance, which is somewhat soluble 

 in water and swells up in dissolving ; it is insoluble in alcohol 

 but readily soluble in alkali, and is strongly dextro-rotatory 

 a D = + 2837-287-6. 



Mannane occurs in salep mucilage, and has been extracted 

 by Ritthausen f and Effront % and others from wheat and 

 barley. Mannanes are also found in Penicillium glaucum, 



* Hessenland: "Z. d. Vereins d. Deut. Zuckerind.," 1892, 42, 671. 

 f Ritthausen: " J. prakt. Chem.," 1867, 102, 321, and " Chem. Zeit.," 1897 

 21, 717. 



JEffront: " Compt. rend.," 1897, 125, 38, 116. 



