424 GRAMINE^E. [PANICUM. 



SDB-TRIBK Avena'cese. Spikelets 2-3-fld., racemed or panicled, axis 

 slender; lowest or all the flowers 2-sexual (except Avena and .!/;/</<- 

 atherum). Empty glumes 2, large, usually much exceeding the flower- 

 ing. Aim. when present usually dorsal, bent, and twisted. 



Fl. glumes (small) usually 2, awned, both 2-sexual 20. Aira. 



Fl. glumes (large) usually 3 or more, awned 21. Avena. 



Fl. glumes (small) 2, awned, upper male 22. Holcus. 



Fl. glumes (small) 3-5, notched or 3-toothed, not awned 23. Triodia. 



SUB-TRIBE Festu'cese. Spikelets racemed or panicled, rarely spiked, 

 2-many-fld. (rarely 1-fla.), axis usually produced beyond the upper 

 palea. Empty glume* usually shorter than the flowering. Lowest 

 flowers or all 2-sexual (except Phragmites). 



A . Fruit not adherent to the palea. 

 1. Axis of spikelet bearded with long silky hairs. 



Lower flower in each spikelet male 24. Phragmites. 



2. Axis of spikelet webbed or glabrous, not bearded. 



o. One or both empty glumes 5- or more-nerved 25. Melica. 



ft. Empty glumes never more than 3-nerved. 

 * Fl. glumes acute ; nerves or converging to the tip. 



Panicle dense, subunilateral. Spikelets compressed 26. Dactylis. 



Panicle contracted, spikelike. Spikelets compressed 27. Koeleria. 



Panicle open. Spikelets terete, conical, coriaceous .23. Molinia. 



** Fl. glumes obtuse or acute ; nerves parallel. 



Fl. glumes compressed, keeled, acute, 5-nerved 29. Poa. 



Fl. glumes cuneate, convex, 5-nerved, tip torn 30. Catabrosa. 



Fl. glumes convex, 5-7-nerved, tip acute or obtuse 31. Glyceria. 



B. Fruit adherent to the palea. 

 * Spikelets all similar, fertile. 



Fl. glumes horizontal, inflated, obtuse 32. Briza. 



Fl. glumes compressed or terete, acute, few-nerved 33. Festuca. 



Fl. glumes compressed or terete, acute, 5-9-nerved 31. Bromus. 



** Outer spikelet of each fascicle deformed, pectinate 35. Cynosurus. 



SUB-TRIBE Hordea'cese. Spikelets 1-many-fld., solitary or 1-3-nate, sessile 

 or subsessile on opposite (rarely on one) sides of a simple rachis ; 

 outer when 3-nate sometimes reduced to a pair of bristle-like glumes. 

 Empty glumes 1-2; awn straight not twisted or 0. 

 * Spike distichous ; Spikelets solitary. 



Empty glumes 2, unequal ; fl. glumes many 36. Brachypodium. 



Empty glumes 2, equal; fl. glumes 2 or more 37. Triticum. 



Empty glume 1 ; fl. glumes many 38. Lolium. 



Empty glumes 2, both facing the rachis ; fl. glumes 1-2 ...39. Lepturus. 

 ** Spike diitichowi ; spikelets 2-3-nate. 



Fl. glumes 2 or more in each spikelet 40. Elymus. 



Fl. glumes 1 or in the lateral spikslets 41. Hordeum. 



1. PAN'ICUM, L. 



Spikelete without bristles at the base, or with slender hairs only, spiked, 

 racemed or panicled, 1-fld., or if 2-fld. the lower male. Empty glumes 2 

 in the 2-fld. spikelets, 3 in the 1-fld. ; lowest small or minute, 2d larger, 



