THE VOLATILE PART OF PLANTS. 69 



Thus, Vauquelia found, or thought he found, 8.5% of 

 this sugar in Odessa wheat. More recently, Peligot, 

 Mitscherlich, and Stein deuied the presence of any sugar 

 in these grains. In his work on the Cereals and Bread, 

 {Die Getreidearten und das Brod, 1860, p. 163), Von 

 Bibra reinvestigated this question, and found in fresh- 

 ground wheat, etc., a" sugar having some of the charac- 

 ters of saccharose, and others of dextrose and levulose. 

 Marcker and Kobus, in 1883, report maltose (which was 

 unknown to the earlier observers) in sound barley, and 

 maltose and dextrose in sprouted barley. 



Von Blbra found in the flour of various grains the f oUowlng quanti- 

 ties of sugar : 



PROPORTIOffS OF SUGAR Df AIB-DRY FLOUR, BRAN, AND MEAL. 



Per cent. 



Wheat flour 2.33 



Spelt flour 1.41 



Wheat bran 4.30 



Spelt bran 2.70 



Rye flour.! . . .-. 3.46 



Eye bran 1.86 



Barley meal 3.04 



Barley bran 1.90 



Oat meal 2.19 



Rice flour 0.39 



Millet flour 1.30 



Maize meal 3.71 



Buckwheat meal 0.91 



Gliicosides. — There occur in the vegetable kingdom a 

 large number of bodies, usually bitter in taste, which 

 contain dextrose, or a similar sugar, chemically combined 

 with other substances, or that yield it on decomposition. 

 Salicin, from willow bark ; pMoridzin, from the bark of 

 the apple-tree root ;.jalapin, from jalap ; aescuUn, from 

 the horse-chestnut, and. amygdalin, in seeds of almond, 

 peach, plum, apple, cherry, and in cherry-laurel leaves, 

 are of this kind. The sugar may be obtained from these 

 so-called glucosides by heating with dilute acids. 



The seeds of mustard contain the glucoside myronic acid united to 

 potassiufln. This, when the crushed seeds are wet with water, breaks 

 up into dextrose, mustard-oil, and acid potassium sulphate, as follows : 

 C,„H„KNS2 0,„ =: CoHijOo + Cs H^ N C S -|- K H S O4 



The cambial juice of the conifers contains coni/erm, crystallizing in 



