14 



Journal of Agricultural Research voi. xvm, No. i 



osazone reaction. Sugar cane has also failed to yield these two sugars. 

 Starch and gums are known to be present; but the latter have not been 

 identified heretofore, although they are held responsible for the failure of 

 sorghum as a source of crystallized sugar. In the sugar cane, Maxwell 

 {ii) found that the "so-called gums" consist largely of pentosans and 

 hexosans. The pentosans are considered to be mostly xylan. 



In the investigations reported here, the ordinary quantitative deter- 

 minations of sucrose, dextrose, and levulose were also taken as means of 

 identification when maltose and raffinose had been proved absent. 

 Sucrose was determined by the Clerget method, and dextrose and levulose 

 by the formula given by Wiley (21, p. 360). The discussion of these 

 sugars will be given in subsections 3 and 4 of this section. 



< 



W 



x5 



W>. 

 k.ff 

 00 



l-S 



III 

 Ki 



ft 

 III 



HO. DAYS FROSa DATi PANICLES 

 APPEARED 



Fig. II. — Development of the ether extract in the various parts of the sorghum plant. 



The investigation of the gums and the nonsugar constituents of the 

 juice was made the subject of a thesis by one of the writers, G. E. Holm. 

 A barrel of juice was obtained from a sorghum factory and preserv^ed by 

 freezing. To a certain degree the juice was concentrated by the freezing, 

 so that the lower portions had a slightly higher specific gravity. This 

 was taken into account, however, in the subsequent analyses. To prove 

 that the freezing did not alter the amount of material precipitated by 

 an equal volume of 95 per cent alcohol, 1,000 cc. of juice were divided 

 into two parts. One part was frozen, then thawed, and then both por- 

 tions precipitated with alcohol. The unfrozen portion yielded i .41 80 gm. 

 dry precipitate, the frozen portion 1.3940 gm. 



That portion of the alcoholic precipitate which would not redissolve in 

 boiling water was subjected to hydrolysis with dilute sulphuric acid for 

 20 hours. It was cooled and filtered, and then the filtrate subjected to 



