GRAMINEAE. 63 



Opening in the flowering: scale turned away from the 

 rachis of the raceme ; spikelets usually oval or orbicular 

 and obtuse, rarely narrower and acute. 



9. Paspalum. 



Opening in the flowering scale turned toward the rachis of 

 the raceme ; spikelets lanceolate to ovate, acute. 



10. Anastrophus. 

 Spikelets of 4 scales. 



Spikelets awnless, the scales glabrous. 



14. Brachiaria. 



Spikelets with the second and third scales hispid on the 

 nerves and usually long-awned, or in one species the third 

 scale only awn-pointed. 15. Echinochloa. 



Racemes long and slender, digitate or whorled, sometimes single or 



in pairs ; spikelets lanceolate and acute. 13. Syntherisma. 

 Spikelets arranged in a true panicle, either open or contracted. 



16. Pamcum. 

 Second scale of the spikelet much enlarged, many-nerved, deeply saccate at the 



base. 17. Sacciolepis. 



Spikelets of two kinds, one borne on terminal panicles, the other solitary on sub- 

 terranean peduncles and maturing seed. n. Amphicarpon. 

 Spikelets subtended by an involucre consisting of : 



i-many persistent bristles ; spikelets in dense spikes or spike-like panicles, deciduous. 



1 8. Chaetochloa. 



2 spine-bearing valves forming a bur enclosing the spikelets and deciduous with 

 them. 19. Cenchrus. 



Tribe V. ORYZEAE. 



Spikelets monoecious ; tall aquatic grasses. 



Pistillate spikelets ovate, borne at the apex of each branch of the panicle. 



20. Zizam'opsts. 

 Pistillate spikelets linear, borne on the upper branches of the panicle, 



21. Zizania. 

 Spikelets not monoecious ; grasses of swamps or wet grounds. 22. Homalocenchrus. 



Tribe VI. PHALARIDEAE. 



Third and fourth scales 



small and empty or rudimentary, not awned ; stamens 3. 23. Phalaris. 



empty, awned upon the back ; stamens 2. 24. Anthoxanthum. 



subtending staminate flowers with 3 stamens ; fertile flowers with 2 stamens. 



25. Savastana. 



Tribe VII. AGROSTIDEAE. 



Flowering scale indurated at maturity, of firmer texture than the empty scales, and closely 



enveloping the grain. 

 Rachilla not prolonged beyond the palet. 



Flowering scale with a three-branched awn ; stamens mostly 3. 



26. Aristida. 

 Flowering scale with a simple awn. 



Flowering scale narrow ; awn persistent. 



Awn tortuous or twisted, stout ; callus evident. 27. Stipa. 

 Awn straight, very slender ; callus minute. 31. Muhlenbergta. 



Flowering scale broad ; awn slender, straight, deciduous : callus obtuse. 

 Flowering scale glabrous, or pubescent with short hairs, 



28. Oryzopsis. 

 Flowering scale pubescent with copious long silky hairs extending much 



beyond the scale. 29. Erwcoma. 



Flowering scale awnless. 30. Milium. 



Rachilla with a pedicel-like extension beyond the palet ; stamens 2. 



32. Brachyelytrum, 



Flowering scale hyaline or membranous at maturity ; empty scales coarser ; grain loose. 

 Spikelets in a dense spike-iike panicle. (Some species of No. 37 may be looked for 

 here.) 



