18 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



Monanthochloe, Distichlis, and a few species of Poa and Eragrostis are 

 dioecious. Gynerium, Cortaderia, Arundo, and Phragmites are tall 

 reeds. In Blepharidachne there is a pair of sterile florets at the base of 

 the single fertile floret, and a rudiment above. In some species of 

 Melica there is, above the fertile florets, a club-shaped rudiment con- 

 sisting of one or more sterile lemmas. In Uniola there are one to four 

 sterile lemmas below the fertile ones. In Melica imperfecta and 

 M. torreyana there may be only one perfect floret. 



Key to the genera of Festuceae 



la. Plants dioecious, (sometimes monoecious), the sexes very dissimilar, the 

 pistillate lemmas with 3 long twisted divergent awns, the staminate lemma 



awnless or mucronate 38. SCLEROPOGON. 



Ib. Plants with perfect flowers, or, if dioecious, the sexes not dissimilar in ap- 

 pearance. 



2a. Lemmas divided at the summit into 5 to several awns or awnlike lobes. 

 Awnlike lobes 5. Inflorescence an erect raceme or simple panicle. 



34. ORCUTTIA. 

 Awns 9 or more. 



Awns unmixed with awned teeth; all the florets falling attached, their 

 awns forming a pappuslike crown, the lower 1 to 3 fertile; panicles 



narrow 37. PAPPOPHORUM. 



Awns mixed with awned teeth; florets not falling attached, the rachilla 



disarticulating between them; panicles somewhat open. 36. COTTEA. 



2b. Lemmas awnless, with a single awn, or, if with 3, the lateral awns minute. 



3a. Tall stout reeds with large plumelike panicles. Lemmas or rachilla with 



long silky hairs as long as the lemmas. 



Leaves crowded at the base of the culms 25. CORTADERIA. 



Leaves distributed along the culms. 



Lemmas naked. Rachilla hairy 26. PHRAGMITES. 



Lemmas hairy. 



Rachilla naked 24. ARUNDO. 



Rachilla hairy 27. NEYRAUDIA. 



3b. Low or rather tall grasses, rarely more than 1.5 m tall. 



4a. Plants dioecious, perennial. Lemmas glabrous; grasses of salt or 



alkaline soils. 

 Plants low, creeping; spikelets obscure, scarcely differentiated from the 



short crowded rigid leaves 18. MONANTHOCHLOE. 



Plants erect from creeping rhizomes; spikelets in a narrow simple ex- 



serted panicle 19. DISTICHLIS. 



4b. Plants not dioecious (except in a few species of Poa with villous lem- 

 mas and in an annual species of Eragrostis) . 

 5a. Spikelets of two forms, sterile and fertile intermixed. Panicle dense, 



somewhat one-sided. 



Fertile spikelets 2- or 3-flowered; sterile spikelets with numerous rigid 



awn-tipped glumes; panicle dense, spikelike 22. CYNOSURTJS. 



Fertile spikelets with 1 perfect floret, long-awned; sterile spikelets 



with many obtuse sterile lemmas; panicle branchlets short, 



nodding 23. LAMARCKIA. 



5b. Spikelets all alike in the same inflorescence. 



6a. Lemmas 3-nerved, the nerves prominent, often hairy. 



7a. Inflorescence a few-flowered head or capitate panicle overtopped 

 by the leaves or partly concealed in them. Lemmas toothed 

 or cleft; low plants of the arid regions. 

 Inflorescence hidden among the sharp-pointed leaves, not woolly; 



plants annual (Chlorideae) 106. MUNROA. 



Inflorescence a capitate woolly panicle, not concealed; plants 



perennial. 



Lemmas cleft either side of the midnerve to near the base, the 

 lower two sterile, the third floret fertile, the fourth reduced 



to a 3-awned rudiment 35. BLEPHARIDACHNE. 



Lemma 2-lobed but not deeply cleft, all fertile but the upper- 

 most- _ _ 31. TRIODIA. 



