32 Proceedings of the Biological Society of Washington. 



Panicle branches ascending ; lower glume lanceolate, 8-9 mm. 



long . vogelianus. 



Panicle branches usually nodding; lower glume smaller, 5-7 

 mm. long. 

 Lower glume elliptic-lanceolate, 6-7 mm. long; awns short or 



wanting effusus. 



Lower glume lanceolate to ovate-lanceolate, 5-6 mm. long; 



awms 12 mm. long . . verticilliflorus . 



Culms stout, usually 1 cm. or more in diameter; sheaths mostly longer 

 than the internodes; panicles rather dense. 



Spikelets falling readily, the glumes very hairy on the back at least 

 when young. 

 Lower glume elliptic-lanceolate, 6-7 mm. long; awns 20-25 mm. 



long; panicle spreading at top abyssinicus. 



Lower glume broadly ovate. 

 Panicle oblong, not very dense; lower glume 6.5-8 mm. long 



cordofanus. 

 Panicle fusiform, very dense; lower glume 5.5 mm. long 



hewisoni. 



Spikelets persistent, the glumes not very hairy on the back even 

 when young. 



Lower glume ovate, very convex, 4-5 mm. long, 7-nerved . niloticus. 

 Lower glume elliptic-lanceolate, not very convex, 5-6 mm. long, 

 11-nerved drummondii. 



Andropogon sorghum exiguus (Forsk.) n. comb. 



Holcus exiguus Forsk. Fl. Aeg.-Arab. 174. 1775. Specimens collected 

 along the banks of the lower Nile. There can scarcely be doubt that 

 this is the same as the succeeding. 



Andropogon sorghum virgatus Hackel in DC. Monogr. Phan. 6:504. 1889. 

 The first of numerous specimens cited is Damietta, Ehrenherg. 



Culms slender, 8-6 or rarely as much as 10 mm. in diameter, erect, 

 usually several from the same root; internodes 5, appressed-pubescent ; 

 leaf-blades narrow, 8-12, rarely 20 mm. broad, 20 to 40 cm. long, green 

 or somewhat purplish tinged, more or less folded, glabrous to the base; 

 panicle narrow, erect or a little nodding at apex, 25-50 or rarely 60 cm. 

 long, with slender erect or ascending liranches, the lower 6 to 10, rarely 

 15 cm. long, naked near the base, less than half the length of the panicle; 

 lower glume of the fertile spikelet slightly indurated, 7 mm. long, 2 mm. 

 broad, narrowly lanceolate, not constricted at base, pale-green, but be- 

 coming straw-colored when fully mature, pubescent with white hairs 

 except on the back, 9-11 nerved, the veins evident above the middle; 

 awns 12 to 16 mm. long, geniculate ; sterile spikelets 6-8 mm. long, nar- 

 rowly lanceolate, but little exceeding the very hairy pedicels ; caryopsis 

 elliptic, flattened, orange-colored, 4 mm. long. 



Kordofan, Kotschy No. 173. (Kew); Near Khartum, Kotschy No. 316, 

 March 1, 1839 (Berlin), a dwarfed form with smaller spikelets; Egedeh 



