106 POACEAE 



Tribe IX. Festuceae. 



Lemmas with 5 awn-like lobes; inflorescence a simple erect raceme. 50. Orcuttia. 



Lemmas awnless or with a single awn. 



Tall stout reeds with large plume-like panicles. 



Lemma clothed with long silky hairs; rachilla naked. 51. Arnndo. 



Lemma naked; rachilla hairy. 52. Phragmites. 



Low or moderately tall grasses, rarely over 1.5 meters tall. 



Plants dioecious, perennial; lemmas glabrous; grasses of salt or alkaline soil. 



Plants low and creeping; spikelets obscure, scarcely differentiated from the short crowded 

 rigid leaves. 49. Monanthochlo'e. 



Plants erect from creeping rhizomes; spikelets in a narrow simple exserted panicle. 



59. Distichiis. 



Plants not dioecious (except in a few species of Poa with villous lemmas and an annual species of 

 Eragrostis). 

 Spikelets of 2 forms, sterile and fertile intermixed. 



Fertile spikelets 2-3-flowered; sterile spikelets with numerous rigid awn-tipped glumes; 



panicle dense and spikelike. 62. Cynosurus. 



Fertile spikelets with one perfect floret, long-awned; sterile spikelets with many obtuse 

 glumes; panicles purple or yellow, contracted. 63. Achyrodcs. 



Spikelets all alike in the same inflorescence. 

 Lemmas 3-nerved. 



Lemmas pilose on the nerves, longer than the glumes; callus densely villous. 



53. Triodia. 

 Lemmas sometimes pubescent but not pilose on the nerves. 



Glumes equaling or exceeding the florets. 54. DissantJielinm. 



Glumes shorter than the first floret. 55. Eragrostis. 



Lemmas 5-many-nerved, the nerves sometimes obscure. 



Lemmas flabellate; glumes wanting; inflorescence dense, cylindric; low annuals. 



56. Anthocltloa. 



Lemmas not flabellate; glumes present; inflorescence not dense and cylindric. 



Palea winged; spikelets linear, in a loose raceme. 58. Pteiiropogon. 



Palea not winged; inflorescence mostly paniculate. 



Lemmas as broad as long, the margins outspread; florets closely imbricate, 



horizontally spreading. 60. Briza. 



Lemmas longer than broad, the margins clasping the palea; florets not horizontally 

 spreading. 

 Callus of florets bearded; lemmas erose at the summit. 64. Fluminea. 

 Callus not bearded (lemmas cobwebby at base in Poa); lemmas not erose 

 (slightly so in Puccinellia). 



Lemmas keeled on the back. 



Spikelets strongly compressed, crowded in 1-sided clusters at the ends 



of the stiff naked panicle branches. 61. Dactylis. 



Spikelets not strongly compressed, not in 1 -sided clusters. 



Lemmas awned from a bifid apex (awnless or nearly so in Bromus 

 unioloides and B. briaaeformis) ; spikelets large. 



69. Bromus. 

 Lemmas awnless; spikelets small. 65. Poa. 



Lemmas rounded on the back (slightly keeled toward the summit in 

 Festuca). 

 Glumes papery; lemmas firm, scarious-margined; upper florets sterile, 

 often reduced to a club-shaped rudiment inclosed by the broad upper 

 lemmas; spikelets tawny or purplish, not green. 



57. Melica. 



Glumes not papery; upper florets not unlike the others. 



Nerves of lemma parallel, not converging at the summit or but 

 slightly so; lemma awnless, mostly obtuse. 



Nerves prominent; glumes nearly as long as the first floret. 



66. Panicnlaria. 

 Nerves faint; glumes much shorter than the first floret. 



67. Puccinellia. 

 Nerves of the lemma converging at the summit; lemmas awned or 



pointed. 



Lemmas entire, awned from the tip or pointed (minutely toothed 



in F. elmeri). 68. Festuca. 



Lemmas awned or awn-tipped from a bifid apex (awnless in B. 



hrizaeformis). ' 69. Bromus. 



Tribe X. Hordeae. 



spikelets solitary at each joint of the rachis (occasionally 2 in Agrol^yron). 

 Si)ikelets placed edgewise to the rachis, the lateral ones with a single glume. 



Spikelets several-flowered. 70. Lolium. 



Spikelets 1-flowered. 71. Leptttrus. 



Spikelets placed flatwise to the rachis, all with 2 glumes. 



Spikelets several-flowered. 74. Agropyron. 



Spikelets 1-flowered; spikes very slender. 



Lemma awnless. 72. Pholiurus. 



Lemma awned. 73. Scnbiiena. 



Spikelets, at least some of them, in twos or threes at each joint of the rachis. 



Spikelets 1-flowered, not all alike, in threes, the lateral pair pediceled. 75. Hordcum. 



Spikelets 2-6-flowered, all alike, usually in twos. 



Glumes minute or wanting; spikes loose. 78. Hystri.v. 



Glumes prominent, mostly narrow; spikes dense. 



Axis of spike continuous, not disarticulating at maturity; glumes broad or narrow but not 

 greatly elongate. 76. Elymus. 



Axis of spike disarticulating at maturity; glumes usually setaceous and elongate. 



77. .Sitainon. 



