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



42. Spikelets 2- to several-flowered (58). 



58. Glumes longer than the lowest floret, usually longer than the 



spikelet (or shorter in genus Sphenopholis with a broadly 



obovate second glume) ; lemmas awnless or awned from the 



back: Tribe Aveneae (59). 



59. Lemmas awnless or sometimes with a very short awn in 



genus Koeleria (60). 



60. Glumes alike, gradually acuminate; spikelets 5- or 6- 



flowered 24. Schismus. 



60. Glumes unlike, the first narrow, the second wider, broad- 

 ened above the middle; spikelets 2- or 3-flowered (61). 

 61. Second glume broadened above the middle, then abruptly 

 narrowed to an acute tip, the first glume narrower 

 but not conspicuously so; lemmas pale and shining; 

 spikelets articulate above the glumes. 



25. Koeleria. 

 61. Second glume broadly obovate, obtuse; lemmas firm, 

 not shining; spikelets articulate below the glumes. 



26. Sphenopholis. 

 59. Lemmas awned (62). 



62. Florets 2, the lower one perfect, awnless, the upper floret 



staminate with a short hooked awn 30. Holcus. 



62. Florets all alike (63). 



63. Spikelets several-flowered; awns conspicuous, flat, bent. 



31. Danthonia. 

 63. Spikelets 2-flowered, sometimes with a rudimentarv 

 third floret (64) . 

 64. Spikelets large, the glumes more than 1 cm. long. 



29. Avena. 

 64. Spikelets small, the glumes much less than 1 cm. long 

 (65). 

 65. Lemmas keeled, awned from above the middle, 



the tip minutely bifid 27. Trisetum. 



65. Lemmas rounded on the back, awned from below 



the middle, the tip erose 28. Deschampsia. 



HS. Glumes shorter than the first floret; lemmas awnless or 

 awned from the tip or from a minutely bifid apex: Tribe 

 Festuceae (66). 

 66. Plants dioecious; pistillate lemmas with 3 long, twisted diver- 

 gent awns, the staminate lemmas mucronate. 



18. ScLEROPOGON. 



66. Plants with perfect flowers or, if dioecious, then the staminate 



and pistillate spikelets similar in appearance (67). 



67. Lemmas divided at summit into 5 or more awns or awnlike 



lobes (68). 



68. Rachilla disarticulating between the florets; summit of 



the lemmas with awns intermixed with awned teeth. 



16. Cottea. 



68. Rachilla not disarticulating between the florets, all 



florets falling attached; summit of the lemmas with 



awns only 17. Pappophorum. 



67. Lemmas awnless, 1-awned or, if 3-awned, then the lateral 

 awns minute (69) . 



69. Tall stout reeds with plumelike panicles (70). 



70. Lemmas hairy; rachilla naked 12. Arundo. 



70. Lemmas naked; rachilla hairy 13. Phragmites. 



69. Low or rather tall grasses; panicles not plumelike (71). 



71. Plants dioecious, the staminate and pistillate spikelets 



similar in appearance; culms erect from creeping 

 rhizomes; plants of saline soiL- 9. Distichlis. 

 71. Plants with perfect flowers (72). 



72. Spikelets of 2 kinds, arranged in fascicles, the ter- 

 minal one 1-flowered, perfect, the others several- 

 flowered, sterile 11. Lamarckia. 



