24 ANALYSIS OF SPECIMENS. 



19. Involucre none, 20 



19. Involucre of two or more bristles 60 — Setaria. 



19. Involucre burr-like, 61— Cenchrus. 



20. PalcEe with awns one to three times their length, 3 — Alopecurus. 



20. Palese with awns five times their length, . . . 44 — ^Hordeum. 



21. Both glumes and paleae awned, 10— Muhlenbergia. 



21. Glumes awnless, single palea awned, 54 — Anthoxanthum. 



21. Palese two, lateral flowers staminate, 53 — Hlerochloa. 



22. Flowers perfect or polygamous, 23 



22. Spikes monoecious, 25 



23. Spikes one-sided 24 



23. Spikes cylindrical, solitary terminal, 4 — Phleum. 



24. Spikes two or more, spikelets suborbicular, . . 58— Paspalum. 



24. Spikes digitate or verticillate, linear 59 — Panicum. 



24. Spikes pedunculate, in a two-sided panicle, . . . 16 — Spartina. 



24. Spikes sessile, in a one-sided panicle, .... 41 — Lepturus. 

 25. Spikes all terminal, sterile above, fertile at base, . . 62 — Tripsacum. 

 25. Fertile spikes lateral, sterile ones terminal panicled 66 — Zea. 



26. Inflorescence in panicles .27 



26. Inflorescence in spikes 39 



27. Flowers awned 28 



27. Flowers without awns, 33 



28. Lower palea awned on the back, 29 



28. Lower palea awned on the apex, 32 



29. Awn near the base of the palea, 30 



29. Awn near the apex of the palea 31 



30. Apex bifid, awn bent 50 — Avena. 



30. Apex bifid, awn bent, lower flower sterile, 51 — Arrhenatherum. 



30. Apex multifid, 47 — Aira. 



31. Palese with two bristly teeth, . 49 — Trisetum. 



31. Palese bifid, 37— Bromus. 



32. Lower palea rounded, obtuse, 35 — Briza. 



32. Lower palea entire, pointed, fruit coated, . . . 36 — Festuca. 



32. Awn between two teeth, twisted, 48 — Danthonia. 



33. Terminal flower perfect, 34 



33. Terminal flower abortive, or a mere pedicel 36 



34. PalesB entire, outer one mucronate, 35 



34. Glumes unequal, like the lower abortive pale, 59 — Panicum. 



34. Glumes equal, longer than the palea, . . . 55 — Phalaris. 



34. Lower palea truncate-muoronate, inner bifid, . . 88 — Uniola. 



34. Flowers silky-bearded on the raohis 39 — Phragmites. 



84. Spikelets terete, palese seven-nerved 31 — Glyceria. 



84. Spikelets two to six, five-nerved 33 — ^Poa. 



34. Spikelets two to twenty, three-nerved, .... 34 — Eragrostis. 



34. Spikelets flat, lower pale laterally compressed, 32 — Brizopyrum. 



