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



several-toothed in Orcuttia, and slightly 2-toothed in Bromus and in a few other 

 genera, the awn, when single, arising from between the teeth. The paleas are 

 persistent upon the continuous rachilla in many species of Eragrostis. Scleropo- 

 gon, Monanthochloe, Distichlis, Hesperochloa and a few species of Poa and 

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

 Neyraudia 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 consisting of 

 1 or more sterile lemmas. In Uniola there are 1 to 4 sterile lemmas below the 

 fertile ones. In Melica imperfecta and M . torreyana there may be only 1 perfect 

 floret. 



Key to the genera of Festuceae 



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

 mas with 3 long twisted divergent awns, the staminate lemma awnless or mucronate. 



41. SCLEROPOGON. 



lb. Plants with perfect flowers, or, if dioecious, the sexes not dissimilar in appearance. 

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



Awnlike lobes 5. Inflorescence an erect raceme or simple panicle 36. Orcuttia. 



Awns 9 or more. 



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

 ing a pappuslike crown, the lower 1 to 3 fertile ; panicles narrow. 

 Spikelets 3-flowered, the first floret fertile; awns 9, plumose, equal. 



40. Enneapogon. 

 Spikelets 4- to 6-flowered, the lower 1 to 3 fertile; awns numerous, not plumose, 



unequal 39. Pappophorum. 



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

 ing between them; panicles somewhat open 38. 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 27. Cortaderia. 



Leaves distributed along the culms. 



Lemmas naked. Rachilla hairy 28. Phragmites. 



Lemmas hairy. 



Rachilla naked..— 26. Arundo. 



Rachilla hairy. 29. Neyraudia. 



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

 4a. Plants dioecious, perennial. 



Plants densely tufted, rather coarse, erect from short rhizomes; lemmas scabrous; 



grasses of dry mountain slopes.. 11. Hesperochloa. 



Plants not densely tufted, spreading by stolons or extensively creeping rhizomes; 

 lemmas glabrous; grasses of salt or alkaline soil. 

 Plants low, stoloniferous; spikelets obscure, scarcely differentiated from the short 



crowded rigid leaves 20. Monanthochloe. 



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



21. DlSTICHLIS. 



4b. Plants not dioecious (except in a few species of Poa with villous lemmas 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 lemmas; panicle dense, spikelike 24. Cynosurus. 



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

 obtuse sterile lemmas; panicle branchlets short, nodding.... 25. 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) 114. Munroa. 



Inflorescence a capitate woolly panicle, not concealed; plants perennial. 

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



