476 CONSTRUCTIVE AND DESTRUCTIVE METABOLISM 



without action on it. Inulin is generally accompanied in the plant by varying 

 amounts of certain allied substances, such as Laevulin, fnu/enin, Synanthrin^. 

 Laevulin occurs in a few plants which contain no inulin, and the same is the 

 case with Triticin, Irisin, Sinistrin, and a few other related carbohydrates 2 . 



Glycogen. Errera 3 and others have shown that glycogen occurs commonly 

 in many fungi. It is a reserve carbohydrate allied to dextrin, and may form in 

 beer-yeast as much as 30 per cent, of the dry weight. Clautriau has shown that 

 in large fungi (Phallus, c.) it is consumed during growth. Yeast is apparently 

 unable to ferment glycogen 4 , but probably, like many other non-fermentable 

 substances, it may be used as food during aerobic existence. Certain contradictory 

 statements may possibly be due to the existence of different varieties of glycogen, 

 although as a matter of fact the glycogen of plants and that of animals appear 

 to correspond very closely with one another. Both form opalescent colloidal 

 solutions with water, and the solution diosmoses so slowly that glycogen can 

 only be extracted from fungi or yeast after the cell-walls have been ruptured. 



Mannite, Trehalose. Mannite is a fairly widely distributed hexahydric alcohol. 

 It is found in various Phanerogams, and is especially abundant in many of the 

 Agaricineae and in mould-fungi s . 



Mannite is often associated in fungi with the polysaccharide trehalose, and in 

 many cases the latter predominates when young, the former when older, the 

 mannite being apparently formed from trehalose. In Agaricuscampestris, \\Q\ie\vc, 

 mannite is present without trehalose, according to Miintz, so that the mode of origin 

 of the former must in this case be different. Similarly Agaricus muscarius 

 produces trehalose but no mannite. Again, Penicillium glaucum always forms 

 mannite, but no trehalose, whether fed with tartaric acid, glucose, starch, or 

 fruit-sap, whereas trehalose is regularly produced by Mucor mucedo. 



No doubt mannite is not always formed or utilized in the same manner by 

 the higher plants : thus the mannite of young olive fruits is according to de Luca 

 converted into oil, whereas Funaro states that mannite first appears in the fruits 

 after the major part of the oil has already been formed 6 . 



On the production of hydrogen during the decomposition of mannite in 

 intramolecular respiration, cf. Sect. 99. 



1 Cf. Tollens, I.e.; Tarnet, Compt. rend., 1893, T. cxvii, p. 50. 



" Cf. Tollens, I.e. According to Brown and Morris (Journ. Chem. Soc., 1893, p. 660), 

 A. Meyer's sinistrin ( Yucca filamentosd} is really inulin. 



3 Errera, Le Glycogene chez 1. Basidiomycetes, 1885 (Mem. d. 1'Acad. roy. d. Belgique, 

 T. xx vn); Laurent, Ann. d. 1'Inst. Pasteur, 1889, T. Ill, p. 116; Clautriau, Etude chim. du 

 Glycogene, 1895. Here the remaining literature is given. 



4 A. Koch u. H. Hosaeus, Centralbl. f. Bact., 1894, Bd. xvi, p. 146 ; M. Cremer, Zeitschr. f. 

 Biol., 1895, Bd. xxxn, p. i. 



* Tollens, 1. c., 1888, p. 266; 1895, p. 281 ; Miintz, Ann. d. chim. et d. phys., 1876, v. ser., 

 T. vn, p. 60; Bourquelot, Bot. Centralbl., 1892, Bd. L, p. 78; Winterstein, Zeitschr. f. physiol. 

 Chemie, 1894, Bd. XXIX, p. 76. 



6 De Luca, Ann. d. sci. nat., 1861, iv. ser., T. xv, p. 92; 1862, iv. sen, T. xvni, p. 125. 

 Cf. the literature given by A. Meyer, Bot. Zeitung, 1886, p. 129; Funaro, Versuchsst., 1880, 

 Bd. xxv, p. 55. 



