8 HISTORY AND DISTRIBUTION OF SORGHUM. 



full key to the principal groups is inserted here. A complete classi- 

 fication of the domestic varieties is in preparation. 



KEY TO THE PRINCIPAL GROUPS OF SORGHUM. 



The following is a key to the principal groups of sorghum : 



I. Pith juicy. 



A. Juice abundant and very sweet. 



1. Intel-nodes elongated; sheaths scarcely overlapping: leaves 12-15 

 (except in Amber varieties) ; spikelets elliptic-oval to obovate, 

 2.5-3.5 mm. wide ; seeds reddish brown. I. Sorgo. 



B. Juice scanty, slightly sweet to subacid. 



1. Internodes short; sheaths strongly overlapping; leaves 12-15; pedun- 



cles erect; panicles cylindrical; spikelets obovate, 3-4 mm. wide; 

 lemmas awnless. II. Kafir. 



2. Internodes medium; sheaths scarcely overlapping; leaves 8-11; 



peduncles mostly inclined, often recurved ; panicles ovate ; spikelets 

 broadly obovate, 4.5-G mm. wide; lemmas awned. VII. Milo. 



II. Pith dry. 



A. Panicle lax, 2.5-7 dm. long; peduncles erect; spikelets elliptic-oval or 



obovate, 2.5-3.5 mm. wide; lemmas awned. 



1. Panicle 4-7 dm. long; rhachis less than one-fifth as long as the 



panicle. 



a. Panicle umbelliform, the branches greatly elongated, the tips 

 drooping; seeds reddish, included. III. Broom corn. 



2. Panicle 2.5-4 dm. long; rhachis more than two-thirds as long as the 



panicle. 



a. Panicle conical, the branches strongly drooping; glumes at ma- 



turity spreading and involute; seeds white or somewhat buff. 



IV. SKallu. 



b. Panicle oval or obovate, the branches spreading: glumes at ma- 



turity appressed, not involute; seeds white, brown, or reddish. 



V. Eowliang. 



B. Panicle compact, 1-2.5 dm. long; peduncles erect or recurved; rhachis 



more than two-thirds as long as the panicle. 



1. Spikelets elliptic-oval or obovate. 2.5-3.5 mm. wide; lemmas awned. 



V. Kowliang. 



2. Spikelets broadly obovate, 4.5-G mm. wide. 



a. Glumes gray or greenish, not wrinkled: densely pubescent; 



lemmas awned or awnless; seeds strongly flattened. 



VI. Durra. 



b. Glumes deep brown or black, transversely wrinkled; thinly pu- 



bescent; lemmas awned; seeds slightly flattened. VII. Milo. 



AGRICULTURAL HISTORY AND DISTRIBUTION OF SORGHUM. 



ORIGIN. 



It is generally conceded that cultivated sorghums were originally 

 derived from the well-known wild species, Andropogon halepensis 

 (L.) Brot. Prof. E. Hackcl (1885) has presented this theory at 

 length, and it is not necessary here to examine his able argu- 



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