80 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



21. Awns stout, conspicuous, 3 to 12 cm. long or, if rather slender, 



then plumose on the lower part; racemes solitary (22). 



22. Awns glabrous or scabrous; primary spikelet fertile, the 



pedicellate one sterile; lower pairs of spikelets all stami- 



nate or neuter 77. Heteropogon. 



22. Awns plumose; primary spikelet sterile, the pedicellate 



one fertile 78. Trachypogon. 



4. Spikelets more or less laterally compressed; sterile florets, if any, above 



the fertile ones (except in tribe Phalarideae) ; articulation above the 



glumes (except in genera Leersia, Sphenopholis, Trisetum, Lycurus, Poly- 



pogon, Alopecurus, and Spartina): Subfamily Festucoideae (23). 



23. Spikelets with two sterile or staminate florets below the fertile one: 



Tribe Phalarideae (24). 



24. Lower florets staminate, as large as the fertile floret, 60. Hierochloe. 



24. Lower florets sterile, reduced to small scales 61. Phalaris. 



23. Spikelets with no sterile florets below the one or more fertile florets (25). 



25. Glumes wanting; pedicels articulate below the 1-flowered spikelets; 



lemma and palea indurate, equal, strongly keeled: Tribe Oryzeae. 



62. Leersia. 

 25. Glumes present (26). 



26. Spikelets sessile or subsessile in spikes or spikelike racemes (27). 

 27. Spikel'et* on opposite sides of the continuous or disarticulating 

 rachis: Tribe Hordeae (28). 

 28. Spikelets solitary at each node of the rachis (29). 



29. First glume present; spikelets placed flatwise to the rachis. 



19. Agropyron*. 



29. First glume wanting except on the terminal spikelet; spike- 



lets placed edgewise to the rachis 23. Lolium. 



28. Spikelets more than one at each node of the rachis (30) . 



30. Spikelets 3 at each node of the rachis, 1-flowered, the lateral 



ones usually reduced to awns 22. Hokdeum. 



30. Spikelets 2 at each node of the rachis (31). 



31. Rachis usually continuous; glumes acute to aristate, entire. 



20. Elymus. 

 31. Rachis readily disarticulating; glumes narrow, extending 



into long divergent awns 21. Sitanion. 



27. Spikelets subsessile on one side of the continuous rachis; spikes 



digitate or racemose on a common axis: Tribe Chlorideae (32). 



32. Inflorescence very small, enclosed in broad, crowded sheaths at 



the ends of the branches 58. Munro a. 



32. Inflorescence distinctly exserted (33). 



33. Plants monoecious or dioecious, or the spikelets unisexual (34) . 



34. Plants with unisexual, rarely perfect florets, the staminate 



and pistillate ones in the same spike_ 57. Cathestecum. 



34. Plants monoecious or dioecious; staminate spikes pectinate, 



the pistillate spikes with the rachis thickened and indu- 

 rate, this together with the second glumes forming a 



false involucre around the florets 59. Buchloe. 



33. Plants with perfect flowers (35). 



35. Spikelets 1-flowered with no rudimentary florets above the 



perfect one (36) . 



36. Spikes digitate 51. Cynodon. 



36. Spikes racemose (37). 



37. Rachilla articulate above the glumes; spikes very slen- 

 der, elongate, widely spreading. 



52. Schedonnardus. 

 37. Rachilla articulate below the glumes, the spikelets 

 falling entire; spikes short and thick; glumes un- 

 equal, the first shorter, the second longer than the 



floret 53. Spartina. 



35. Spikelets 2- to several-flowered or, if only 1-flowered, then 

 with 1 or more rudimentary florets above the fertile 

 one (38). 

 38. Spikes solitary or racemose (39) . 



39. Lemmas entire or minutely bifid, awnless or 1-awned; 

 spikelets with 2 to several perfect florets. 



49. Leptochloa. 



