154 A TEXT-BOOK OF BOTANY. 



is more rapid they are nearly colorless and dissolve readily. The 

 crystals of hesperidin are insoluble in water, alcohol, glycerin, 

 ether, chloroform, solutions of hydrated chloral, dilute sulphuric 

 acid and dilute or concentrated hydrochloric acid and nitric acid. 

 They are sparingly soluble in ammonia water and hot acetic acid. 

 Upon the addition of either dilute or concentrated solutions of 

 potassium hydroxide or sodium hydroxide, hesperidin dissolves, 

 forming a yellowish solution. With concentrated sulphuric acid 

 it gives a deep yellowish solution, \vhich upon warming becomes 

 a reddish-brown. Sometimes hesperidin, as in the stamen hairs 

 of Verbascum, is colored with concentrated sulphuric acid only 

 a light yellow. 



GLYCOGEN is a carbohydrate allied to amylo-dextrin and occurs 

 commonly as a reserve food material in the fungi and some 

 of the Cyanophycecc. It usually occurs in the form of a more or 

 less amorphous mass in the hyph;e of the fungi, but occasionally 

 is found in definite granules resembling starch. It is supposed 

 to arise in plastid bodies resembling leucoplastids, but its general 

 formation is controlled by the protoplasm. In yeast it is found 

 in large quantities, sometimes nearly filling the entire cell. 



CRYSTALLINE SUBSTANCES. 



The sugars constitute a group of crystalline principles of 

 wide distribution. They occur in the cell-sap, from which by 

 evaporation or on treatment with alcohol they may be crystallized 

 out. There are chemically two main groups : monosaccharoses 

 (formerly termed glucoses) and disaccharoses (formerly the 

 saccharoses). Under the former are included the simple sugars 

 containing two or more atoms of carbon and known as biose 

 (C 2 H 4 O 2 ), etc. Among the pentoses (QH 10 O 5 ) are rhamnose, 

 a component of certain glucosides ; fucose, found in fucus and 

 other brown algae, and chinovite, occurring in certain Cinchona 

 barks. The most important subdivision of the monosaccharoses 

 comprises the hexoses (CoH^O,.), which include glucose and 

 fructose, and are widely distributed ; d-mannose, found in the 

 manna of Fra.vimis Omits and obtained by hydrolyzing cellulose, 

 especially the reserve cellulose in the seeds of the vegetable ivory. 

 Of the disaccharoses (C^Il,,* ),, ) cane-sugar is the most im- 



