GENERA OF GRASSES OF THE UNITED STATES. 
0 
Key to the genera of Festuceae. 
la. Plants dioecious, the sexes very dissimilar, the pistillate lemmas with 
3 long twisted divergent awns, the staminate lemma awnless 
or mucronate 30. Scleropogon. 
lb. Plants with perfect flowers, or, if dioecious, the sexes not dissimilar 
in appearance 2 
2a. Lemmas divided at the summit into 5 to several awns or awn- 
like lobes 3 
3a. Awnlike lobes 5 ; inflorescence a simple erect raceme- 29. Orcuttia. 
3b. Awns 9 or more 4 
4a. Awns unmixed with awned teeth ; all the florets falling 
attached, their awns forming a pappuslike crown, only • 
the lowest floret fertile ; panicles narrow- 32. Pappophorum. 
4b. Awns mixed with awned teeth ; florets not falling at- 
tached, the rachilla disarticulating between them ; 
panicles somewhat open 31. Cottea. 
2b. Lemmas awnless, with a single awn, or, if 3, the lateral awns 
minute 5 
5a. Tall stout reeds with large plumelike panicles; lemmas or 
rachilla with long silky hairs as long as the lemmas G 
6a. Lemmas hairy ; rachilla naked 19. Arundo. 
6b. Lemmas naked ; rachilla hairy 20. Phragmites. 
5b. Low or rather tall grasses, rarely over 5 feet tall 7 
7a. Plants dioecious, perennial; lemmas glabrous; grasses 
of salt or alkaline soils 8 
8a. Plants low and creeping; spikelets obscure, scarcely 
differentiated from the short crowded rigid 
leaves 16. Monanthochloe. 
8b. Plants erect from creeping rhizomes; spikelets in a 
narrow simple exserted panicle 17. Dtstichlis. 
7b. Plants not dioecious ( except in a few species of Poa with 
villous lemmas and in an annual species of Eragrostis) _ 9 
9a. Spikelets of two forms, sterile and fertile intermixed ; 
panicle dense, somewhat one-sided 10 
10a. Fertile spikelets 2 or 3 flowered ; sterile spike- 
lets with numerous rigid awn-tipped glumes ; 
panicle dense and spikelike 22. Cynostjrtjs. 
10b. Fertile spikelets with 1 perfect floret, long- 
awned; sterile spikelets with many obtuse 
glumes ; panicle branchlets short, nodding. 
23. Achyrodes. 
9b. Spikelets all alike in the same inflorescence 11 
11a. Lemmas 3-nerved, the nerves prominent, often 
hairy 12 
12a. Inflorescence a few-flowered head or capi- 
tate panicle overtopped by the leaves or 
partly concealed in them ; lemmas toothed 
or cleft ; low plants of the arid regions— 13 
13a. Inflorescence hidden among the sharp- 
pointed leaves, not woolly; plants 
annual (Chlorideae) 97. Munroa. 
13b. Inflorescence a capitate woolly panicle, 
not concealed ; plants perennial 14 
