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 nve 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 staininate, 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. 



81. 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. Palese entire, outer one mucronate, 36 



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



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



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



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



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



34. 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. 



