12 GRAMINEAE 



b. Spikelets a-many-flowered. 

 Flowering scales usually shorter than the empty ones, the awn dorsal 



and usually bent. Tribe VIII. AVENEA.B. 



Flowering scales usually longer than the empty ones, the awn terminal 

 and straight, rarely dorsal, sometimes wanting. 



Trlbe X. FESTUCEAE. 

 B. Spikelets in two rows : 

 On one side of the continuous axis, forming one-sided spikes or racemes. 



TribkIX. CHLORIDEAE. 

 On opposite sides of an axis which is often articulated, forming equilateral 

 spikes. Tribe XI. HORDEAE. 



Tribe I. MAYDEAE. 

 Fertile spikelets imbedded in the internodes of the thick rachis. 



I. Trips ACUM. 



Tribe II. ANDROPOGONEAE. 

 Spikelets alike, perfect. 2. Erianthtis. 



Spikelets not alike, the sessile perfect, the pedicellate imperfect or wanting. 

 Inflorescence of spike-like silky racemes. 3. Andropogon. ) 



Inflorescence paniculate. 

 Pedicellate spikelets present and usually staminate. 



4. Sorghum. 

 Pedicellate spikelets wanting. 5. Sorghastrum. 



[Tribe III. ZOYSIEAE. 

 A single genus is our range. 6. Nazia. 



Tribe IV. PANICEAE. 



A. Spikelets naked, not involucrate. 

 Empty scales 2. 



Spikelets ovate to orbicular, usually obtuse, rarely acute. 



7. Paspalum. 

 Spikelets lanceolate, acute to acuminate. 8. Syntherisma. 



Empty scales 3. 

 Empty scales not awned. 

 Spikelets in very slender one-sided racemes which are usually whorled 



or approximate. 8. Syntherisma. 



Spikelets in panicles or panicled racemes, the latter never whorled, com- 

 monly distant. 10. Panicum. 

 Empty scales awned or awn-pointed. 9. Echinochloa. 



B. Spikelets involucrate. 



Involucre of numerous bristles. 11. Chaetochloa. 



Involucre of two spine-bearing valves. 12. Cenchrus. 



Tribe V. ORYZEAE. 

 Spikelets monoecious. 13. Zizania. 



Spikelets perfect. 14. Homalocenchrus. 



Tribe VI. PHALARIDEAE. 

 Third and fourth scales awnless. 15. Phalaris. 



Third and fourth scales awned on the back. 16. Anthoxanthum. 



Tribe VII. AGROSTIDEAE. 

 A. Flowering scale indurated when mature and very closely embracing the 

 grain, or at least firmer than the empty scales. 



