24 ANALYSIS OP SPECIMENS. 



19. Involucre none, ...20 



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



19. Involucre burr-like, 61— Cenchrus. 



aO. FalesB with awns one to three times their length, 3 — Alopecurus. 



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



21. Both glumes and palesB awned 10— Muhlenbergia. 



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



21. Paleaa two, lateral flowers staminate, 63 — Hierochloa. 



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 — ^Paspaliim. 



24. Spikes digitate or verticillate, linear 59 — ^Panioum. 



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



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



25. Spikes all terminal, steiile 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. Paleaa with two bristly teeth, 49 — Trisetum. 



31. Palese bifid 37— Bromua. 



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



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



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



83. Terminal flower perfect, 34 



33. Terminal flower abortive, or a mere pedicel 36 



34. Paleee entire, outer one mucronate, 35 



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



34. Glumes equal, longer than the palea 65 — Phalaris. 



' 34. Lower palea truncate-mucronate, inner bifid, . . 38 — Uniola. 



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



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



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



34. Spikelets two to twenty, three-nerved, .... 34 — ^Eragrostia. 



84. Spikelets flit, lower pale laterally compressed, 32 — ^Brizopyrum. 



