140 PLANT PHYSIOLOGY 



stamps, where one can recognize the faintly sweetish taste of the 

 achroodextrin and the glucose. 



Glycogen or " animal starch" is the common form of starch 

 stored in the animal body. The liver is a glycogen storehouse 

 but, although so common in animals, glycogen is much rarer in 

 plants, where it is found chiefly in the fungi. Evidently there 

 is some connection between the heterotrophic form of nutrition 

 and the kind of carbohydrate stored. Yeast cells are especially 

 rich in glycogen, which may account for some of the good results 

 obtained from yeast in the animal diet. Glycogen resembles 

 amylodextrin or soluble starch in its properties and on hydrolysis 



yields glucose. 



Lichenin from lichens, paradextrin from a mushroom, Boletus 

 edulis, and para-isodextrin from another fungus, Polyporus betu- 

 linus, are dextrosans which much resemble starch but which are 

 of small economic importance. When hydrolyzed, lichenin yields 

 cellobiose just as cellulose does. 



The levulosans are built up from levulose in the same way that 

 the dextrosans are built up from dextrose. Of these, by far the 

 most important is inulin, which is found in many plants as the 

 regular storage product. It occurs especially in the Composite 

 (artichoke, chicory, and dahlia) but has been reported from many 

 other families. In monocots, it has been observed that those in 

 moist places tend to form starch, while those in the drier places are 

 more likely to form inulin. This levulosan is a white, tasteless 

 powder soluble in water, from which it may be precipitated by 

 alcohol in the form of spherocrystals. It is levorotary and is 

 hydrolyzed in the plant by (the enzyme) inulase to form fructose. 



Other levulosans of minor importance in plants are graminin 

 from grasses, irisin from Iris, phlein from timothy, sinistrin 

 from Scilla, and triticin from Triticum repens, which from their 

 gummy nature and general behavior are thought to correspond to 



dextrins. 



Mannosans are polysaccharides which contain mannose, but 

 most of these also contain other sugars such as galactose and 

 dextrose. They are found in many plants as reserve food materials, 

 e. g., in the leaves and wood of many trees such as the chestnut, 

 apple, mulberry, and conifers. The seeds of many palms including 

 the vegetable ivory palm contain in the hard outer walls these 

 mannosans in combination with cellulose, with the result that 



