POACEAE. 



11 



* Spikelets in clusters of 3 or 4, the empty scales 



forming a false involucre. 

 ** Spikelets otherwise arranged. 



t Spikelets not sunken in the rachis. 



J Spikelets without a subtending involucre 



of bristles or valves. 

 Scales awnless. 



Fruiting scale chartaceous, the mar- 

 gins hyaline and flat. 

 Racemes in whorls, or approximate 

 at the summit of the stem ; outer 

 scales of the spikelet with short 

 hairs or glabrous. 



Racemes on an elongated axis ; 

 outer scales of the spikelet 

 clothed with long hairs exceed- 

 ing the spikelet. 



Fruiting scale indurated, rigid, the 



margins inrolled and not hyaline. 



Opening in the fruiting scale turned 



toward the rachis. 

 Opening in the fruiting scale turned 



away from the rachis. 

 Spikelets plano-convex, arranged 

 in secund racemes, of 3 scales. 

 Spikelets unequally bi-convex, 

 in panicles, or rarely in 

 secund racemes, of 4 

 scales. 



Culms herbaceous. 

 Culms woody. 



Scales, or some of them, awned or awn- 

 pointed. 



Third scale awned or awn-pointed, the 

 second and first scales awnless or 

 with awns successively shorter. 

 Third scales awnless or awn-pointed, 

 the second and first scales with 

 awns successively longer. 

 $t Spikelets with an involucre. 

 Involucre of bristles. 



Bristles persistent ; spikelets de- 

 ciduous. 



Bristles deciduous with the spikelets. 

 Involucre of 2 spine-bearing valves. 

 ft Spikelets sunken in one side of a flat thick 



rachig. 

 B. Spikelets articulated above the empty persistent scales, 



1-many-flowered. 



1. Stems' herbaceous, hence annual ; leaves scattered. 

 * Spikelets of 3 scales, 1-flowered. 



Flowering scale awned, closely embracing the grain. 

 Awns 3. 

 Awn 1. 

 Flowering scales awnless, the grain dropping from 



it when mature. 

 ** Spikelets of 4 or more scales, usually with 2 or more 



flowers. 

 t Spikelets in 2 rows, forming 1-sided spikes or 



racemes. 



Spikelets wholly deciduous. 

 Spikelets not wholly deciduous. 



1 perfect flower in each spikelet. 



No empty scales above the flowers. 

 1-several empty scales above the flower. 

 Spikes in whorls or closely approxi- 

 mate. 



Second empty scale acute ; awn of 

 the flowering scales usually long. 

 Second empty scale truncate or 2- 

 toothed ; flowering scales awnless 

 or awn-pointed. 

 Spikes remote. 



2-several perfect flowers in each spikelet. 

 Spikelets densely crowded ; spikes digitate. 

 Spikes with terminal spikelets. 

 Spikes with the rachis extending 

 beyond the spikelets in a naked 

 point. 



6. Anthcphora. 



1. Syntherisma. 



8. Valota. 



9. Axonopus. 

 10. Paspalum. 



11. Panicum. 



12. Lasiacis. 



13. Echinochloa. 



14. Oplismenus. 



15. OhaetocMoa. 



16. Cenchropsis. 



17. Cenchrus. 



18. Stenotaphrum. 



19. Aristida. 



20. Muhlenbergia. 



21. Sporobolus. 



22. Spartina. 



23. Capriola. 



24. Chloris. 



25. Eustachys. 



26. Bouteloua. 



27. Eleusine. 



28. Dactyloctenium. 



