Grasses of Porto Rico t\7\ 



FIoweriiiR scale witli its openinc; turned toward the rachis. 



lO. Atiastroplius. 

 Scales 4. 



Perfect flowers 2. il. Isachnc. 



Perfect flower i. 



Second empty scale not saccate at the base. 

 Empty scales not awned. 



Spikelets in very slender I -sided racemes which are 

 usually whorled or approximate. 



12. Synt/ietisnin. 

 Spikelets in panicles or panicled racemes, the latter 



never whorled, commonly distant. 

 Spikelets long-hairy, acuminate. 



13. Trichachnc. 

 Spikelets glabrous or with only short hairs 



usually orbicular to ovate, if lanceolate 

 glabrous. 

 Spikelets hemispheric, orbicular or nearly so 

 in outline, the rachisof the l-sided racemes 

 winged. 14. Dimorp/iostac/iys. 



Spikelets not hemispheric, varying in outline, 

 usually in panicles, rarely in racemes 

 and then the rachis not winged. 

 Flowenng scale without lateral pits or ap- 

 pendages at the base. 



15. Panicuvi. 

 Flowering scale with pits or membra 



nous appendages at the base. 



16. Ichnanthus. 

 Empty scales awned or awn -pointed. 



Stems creeping : leaf-blades short and broad. 



17. Oplismcnus. 

 Stems erect : leaf-blades long and narrow. 



18. Ecltiiiochloa. 

 Second empty scale saccate at the base. 19. Sacciohpis. 



** Spikelets involucrate. 



Involucre of bristles. 20. Chactochloa. 



Involucre of 2 spine-bearing valves. 21. Cenchrus. 



b. Spikelets .sunken in one side of the broad flattened rachis. 22. Steitotaphriim. 



2. Spikelets monoecious : leaf-blades with a petiole-like base. 23. Olyra. 



Tribe VI. Oryzkae 

 Grasses with broad flat leaf-blades and long narrow spikelets. 24. Pharus. 



Tribe VII. Ar.ROSTinEAE 



Flowering scale with three long awns. 25. Aristida. 



Flowering scale awnless. 26. Sporobolus. 



Tribe VIII. Chlorideae 



I. Spikelets with i perfect flower. 

 Spikes digitate or in whorls. 



