20 POACEAE. 



Empty glumes generally 



shorter than the flowering 



glumes, these awnlcss or 



with 1-many terminal, 



rarely dorsal straight or 



simply divergent awns. Tribe 7. Festuceae. 

 Spikelets sessile in true spikes or 



on very short pedicels in 



unilateral racemes. 

 Spikelets in unilateral spikes 



or racemes. Tribe 6. Chlorideae. 



Spikelets inserted on the 



alternate notches of the 



rachis forming equilateral, 



flattened or cylindric spikes. 



Tribe 8. Hordeae. 



Tribe 1. ANDROPOGONEAE. Sorghum Tribe. 



Spikelets in spike-like racemes, 2 at each joint of the 

 rachis, 1 pedicellate and hermaphrodite, staminate or 

 rudimentary. Glumes usually 4, the first and second 

 empty, large and much firmer in texture than the others, 

 the third usually empty or with a staminate flower in 

 its axil, rarely awned, the fourth or flowering glume 

 hyaline, usually awned, the awn generally twisted or 

 geniculate. 



Inflorescence composed of spike-like silky racemes. 1. Andropogon. 

 Inflorescence paniculate; spikelets somewhat silky- 

 pubescent. 2. HoLCUS. 



1. ANDROPOGON L. 



Slender or rather coarse perennials with solid culms. 

 Spikelets heterogamous, in pairs at each joint of the 

 articulate and usually hairy rachis, one of each pair ses- 

 sile, hermaphrodite and 1 -flowered, the other pedicellate 

 and staminate or rudimentary. Glumes of the fertile 

 spikelet 4, the first coriaceous, flattened on the back with 

 a strong nerve near each margin and usually with 

 fainter ones between, second glume hyaline, awned. 

 Stamens 3. Styles distinct; stigmas plumose. Grain 

 unfurrowcd, free within the hardened outer glumes. 



1. A. glomeratus (Walt.) B. S. P. Culms erect, 4-6 dm. high, 

 smooth, simple below, much branched above, upper nodes of branches 



