24 ANALYSIS OF SPECIMENS. 



19. Involucre none, 20 



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



19. Involucre burr-like, 61 Cenchrus. 



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



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



21. Both glumes and palese awned, 10 Muhlenbergia. 



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



21. Paleae 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. 



82. Awn between two teeth, twisted 48 Danthonia. 



33. Terminal flower perfect, 34 



83. Terminal flower abortive, or a mere pedicel, 36 



34. Paleae entire, outer one mucronate 35 



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



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



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



84. Flowers silky-bearded on the racliis 39 Phragmites. 



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



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



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



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



