24 ANALYSIS OF SPECIMENS. 



19. Involucre none, 20 



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



19. Involucre burr-like 61 Cenchrus. 



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



20. Paleae 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. Paleoe two, lateral flowers staminate 53 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 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. 



81. Paleae with two bristly teeth 49 Trisetum. 



31. Paleae 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 



83. Terminal flower abortive, or a mere pedicel 36 



84. Paleae entire, outer one mucronate, 35 



84. Glumes unequal, like the lower abortive pale, 59 Panicum. 



84. Glumes equal, longer than the palea, 55 Phalaris. 



84. Lower palea truncate-mucronate, inner bifid, . . 38 Uniola. 



84. Flowers silky-bearded on the rachis, .... 39 Phragmites. 



84. Spikelets terete, paleae seven-nerved, 31 Glyceria. 



84. Spikeleta 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. 



