62 CHEMISTRY OF PLANT LIFE 



(specific rotatory power +190), is colored brown by iodine, and is 

 hydrolyzed to dextrin and maltose, and finally to glucose. 



Lichenin, para dextran, and para isodextran are dextrosans 

 which have been isolated from various lower plants. They all 

 yield glucose when completely hydrolyzed. They resemble 

 starch in chemical properties, but differ from it in physical form, 

 etc. 



(B) LEVULOSANS 



Inulin replaces starch as the reserve food carbohydrate in a 

 considerable number of natural orders of plants, particularly in 

 the Compositae. It is the carbohydrate of the tubers of the 

 dahlia and artichoke and of the fleshy roots of chicory. It is often 

 found associated with starch in monocotyledonous plants, such as 

 many species of Iris, Hyadnthus, and Muscari. Among the mono- 

 cotyledons, starch seems to be the characteristic carbohydrate 

 reserve of aquatic, or moisture-loving, species, while inulin is 

 more common among those which prefer dry situations. 



Inulin may be prepared from the tubers of dahlias or arti- 

 chokes, by boiling the crushed tubers with water containing a little 

 chalk (to precipitate mineral salts, albumins, etc.) filtering and 

 cooling the filtrate practically to the freezing point, which precipi- 

 tates the inulin. 



Inulin is a white, tasteless, semi-crystalline powder, which is 

 soluble in hot water, from which it may be precipitated by alcohol 

 or by freezing. It forms no paste like that of starch or dextrin, 

 and gives no color with iodine. It is levorotatory, and when 

 hydrolyzed by acids or by the enzyme inulinase yields fructose; 

 in fact, inulin bears the same relation to fructose that starch does 

 to glucose. 



Graminin, irisin, phlein, sinistrin, and triticin are all inulin- 

 like polysaccharides, which have been found in the plants after 

 which they are named. Their solutions are, as a rule, sticky or 

 gummy in consistency, which suggests that these compounds 

 bear the same relation to inulin that dextrins do to starch. 



(C) MANNOSANS, OR MANNANS 



Mannan bears the same relation to mannose that starch does to 

 glucose and inulin to fructose. It occurs as a reserve food sub- 



