100 POACEAE 



Lemma scabrous or glabrous. 



Empty glumes lanceolate, acuminate or short-awned, 2-5-nerved. 

 Spike dense; spikelets more or less imbricate. 



Plants not tufted, with rootstocks; leaf-blades spreading. 



Sheaths and blades glabrous; glumes scabrous, at least above. 



10. E. glaucus. 

 Sheaths and lower leaf-blades pubescent; glumes glabrous. 



11. E. marginalia. 

 Plants tufted; leaf-blades ascending. 12. E. nilidus. 



Spike lax; spikelets distant; glumes glabrous. 13. E. Petersonii. 



Empty glumes linear-subulate. 



Spike 7-8 mm. thick; awns 30-40 mm. long. 14. E. Saundersii. 



Spike 5 ram. thick; awns 5-10 mm. long. 15. E. Macounii. 



Lemma awnless or short-awned; awn less than one-third the length of the body. 

 Empty glumes strongiy 3-5-nerved. 



Empty glumes thickened and strongly curved at the base, not scarious-margined. 



16. E. curvatus. 

 Empty glumes neither thickened nor strongly curved at the base, more or less 



scarious-margined. 17. E. Howellii. 



Empty glumes 1-nerved or indistinctly 3-nerved. 

 Lemma glabrous or hispidulous 



Empty glumes aristiform or narrowly subulate. 



Plant stout, 1-2 m. high, tufted; spikelets 2-6 at each joint; lemma scab- 



rous-hispidulous. 18. E. condensatus. 



Plant slender, 3-10 dm. high; spikelets 1 or 2 at each joint. 



Lemma broadly lanceolate, acute or awn-pointed; rachis scabrous on 

 the sharp angles; spikelets erect; plant with a horizontal root- 

 stock. 19. E. triticoides. 

 Lemma narrowly lanceolate; rachis nearly terete, strigose; plant tufted. 

 Spikelets usually in pairs; lemma awn-pointed. 



Lemma glabrous. 20. E. ambiguus. 



Lemma scabrous or scabro-strigose. 21. E. strigosus. 



Spikelets usually singly; lemma acuminate or acute. 



22. E. salinus. 

 Empty glumes lanceolate-subulate, tapering from the rather broad base; 



lemma glabrous. 23. E. simplex. 



Lemma pubescent. 



Plants tufted; lemma long-attenuate, short-awned. 24. E. rilliflorus. 



Plants not tufted, or somewhat so in E. cinercus, with horizontal rootstocks; 



lemma not long-attenuate. 

 Lemma appressed-pubescent. 



Stem, sheath, and leaves glabrous or minutely strigulose. 



25. E. arenicola. 



Stem, sheath, and leaves densely short pubescent. 26. E. cinereus. 

 Lemma with spreading pubescence. 



Spike long; empty glumes lanceolate, silky-villous. 



27. E. flavescens. 

 Spike short; empty glumes subulate, scabrous. 28. E. innovatus. 



1. E. virginicus L. Stem 6-10 dm. high; sheath usually glabrous; leaf- 

 blades 1-3 dm. long, 4-16 mm. wide, scabrous; spike 5-15 cm. long, thick, erect; 

 lemma 6-8 mm. long, glabrous; awn scabrous, 5-18 mm. long. Along streams: 

 N.S. Fla. Tex. Sask. Plain. Je-Au. 



2. E. jejunus (Ramaley) Rydb. Stem slender, 3-6 dm. high; leaf-blades 

 1-2 dm. long, 2-5 mm. wide, scabrous; spike 2-6 cm. long, strict; spikelets usually 

 2 at each node; lemma lanceolate, 7-8 mm. long, scabrous, hispidulous; awn 3-10 

 mm. long. E. virginicus minor Vasey. E. virginicus jejunus Ramaley. Sand 

 hills and river banks: Minn. 'Neb. Wyo. Mont. Plain Submont. Je-Au. 



3. E. diversiglumis Scribn. <t Ball. Stem 9-12 dm. high, glabrous; leaf- 

 blades spreading, 1.5-2.5 dm. long, 6-12 mm. wide, scabrous on both sides; 

 spikelets in pairs, 2-flowered; lemma linear-lanceolate, acute, 8-10 mm. long, 

 indistinctly 3-5-nerved, hirsute or scabrous, hispidulous; awn 2-3 cm. long. Rich 

 open places: Wis. Wyo. N.D. Plain Submont. 31. 



4. E. canadensis L. Stem 6-15 dm. high, glabrous; leaf-blades 1-3 dm. 

 long, 4-20 mm. wide, scabrous; spike 1-3 dm. long, usually long-exserted, nod- 

 ding; spikelets spreading, 3-5-flowered ; lemma 8-14 mm. long; awn 2-5 cm. long, 

 rough. River banks and among bushes: N.S. Ga. N.M. B.C. Plain- 

 Submont. Jl-Au. 



5. E. robustus Scribn. & Smith. Stem 1-2 m. high, smooth; leaf -blades 

 2-4 dm. long, 8-20 mm. wide, scabrous on both sides; spike 12-18 cm. long, 2.5- 

 4 cm. thick; spikelets 3-4 at the nodes, 3-4-flowered; lemma 12-16 mm. long, 



