GRASSES OF Porto Rico 371 
Flowering scale with its opening turned toward the rachis. 
10. Anastrophus. 
a Scales 4. 
¥ Perfect flowers 2. 11. Lsachne. 
Perfect flower 1. 
Second empty scale not saccate at the base. 
Empty scales not awned. 
Spikelets in very slender 1-sided racemes which are 
usually whorled or approximate. 
12. Syntherisma, 
Spikelets in panicles or panicled racemes, the latter 
never whorled, commonly distant. 
Spikelets long-hairy, acuminate. 
13. Zrichachne. 
Spikelets glabrous or with only short hairs, 
usually orbicular to ovate, if lanceolate 
glabrous. 
Spikelets hemispheric, orbicular or nearly so 
in outline, the rachis of the I-sided racemes 
winged. 14. Dimorphostachys. 
Spikelets not hemispheric, varying in outline, 
usually in panicles, rarely in racemes 
and then the rachis not winged. 
Flowering scale without lateral pits or ap- 
pendages at the base. 
15. Panicum, 
Flowering scale with pits or membra- 
nous appendages at the base. 
16, Jchnanthus. 
Empty scales awned or awn-pointed. 
Stems creeping : leaf-blades short and broad. 
17. Oplismenus. 
Stems erect: leaf-blades long and narrow. 
18. Echinochloa. 
} Second empty scale saccate at the base. 19. Sacciolepis. 
** Spikelets involucrate. 
Involucre of bristles. 20. Chaetochloa, 
Involucre of 2 spine-bearing valves. 21. Cenchrus. 
b. Spikelets sunken in one side of the broad flattened rachis. 22. Stenotaphrum. 
2. Spikelets monoecious: leaf-blades with a petiole-like base. 23. Olyra. 
Tribe VI. OnYZEAE 
Grasses with broad flat leaf-blades and long narrow spikelets. 24. Pharus. 
Tribe VII. AGROSTIDEAE 
Flowering scale with three long awns. 25. Aristida, 
Flowering scale awnless. 26. Sporobolus. 
Tribe VIII. CHLORIDEAE 
1. Spikelets with 1 perfect flower. 
Spikes digitate or in whorls. 
