290 Alary Davies Swartz, 



The most extensive study has been given to the mannans of various 

 seeds, in which, as already shown, ^ mannans and galactans seem al- 

 most invariably to occur together. The seeds of the carob tree {Ce- 

 ratonia siliqua) contain a hemicellulose originally called "caruban" 

 by Effront (241) (1897), but shown by van Ekenstein (282) to yield 

 mannose, and by Bourquelot and Herissey (232) (1899), (^-galactose. 

 The first elaborate studies of "reserve-cellulose" were made by Reiss 

 (264), who showed that the horny albumen of the seeds of Phytelepas 

 macrocarpa, Phoenix dactylifera and other species of palm, Allium 

 cepa, Asparagus officinalis, Iris pseudacorus, Strychnos nux vomica 

 and Caffea arabica, differed chemically from true cellulose in their 

 color reactions, in the ease with which they can be hydrolyzed, and in 

 yielding, instead of dextrose, a sugar which he called "seminose," 

 but which proved to be identical with Fischer and Hirschberger's (242) 

 previously described mannose. 



Mannan also occurs richly in the tubers of the many species of Or- 

 chis and Eulophia which are the source of commercial salep. On ex- 

 traction with water, they yield a mucilaginous extract which was 

 first studied by C. Schmidt (270) in 1844, and called by him "salep- 

 bassorin"; on hydrolysis with dilute sulphuric acid he obtained, be- 

 s'des some gummy substance and cellulose, a fermentable sugar 

 which he thought to be dextrose. Mulder (259) considered the salep 

 mucilage a mixture of starch and gum or pectin acids, while Franck 

 (243) thought it a modification of cellulose, and Girand (248) a trans- 

 formation of a starchy substance into a variety of dextrin swelling in 

 water. Pohl (263) by precipitation with neutral salts, distinguished 

 an "a-Schleim" and a "j8-Schleim. " According to Thamm (276), who 

 has made the most recent investigations, "a-Schleim" does not occur 

 in German salep. ToUens and Gans (277) showed that on hydrolysis, 

 besides dextrose, mannose or, as they called it, " isomanitose " was 

 formed, but this was shown by Fischer and Hirschberger (242) to be 

 identical with J-mannose. Thamm (276) and Hilger (254) have shown 

 conclusively, that the starch-free water extract contains an anhydride 

 of mannose only. 



A very resistant type of mannan occurring in some plants, has been 

 designated as manno-cellulose by Schulze (273). Bertrand (227) 

 finds it taking the place of xylan in the woody tissues of gymnosperms. 



^Cf. Schulze and his coworkers, and Goret, under Galactans. Also Schulze and 

 Godet, Zeitschrift fiir physiologische Chemie, V. 61, p. 279, for a very coraplete 



