100 POACEAE 



Lemma sC£.brous or glabrous. 



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

 Spike dense: spikelefs more or less imbricate. 



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



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



10. E. (jloucus. 

 Sheaths and lower leaf-blades pubescent; glumes glabrous. 



11. E. marginalia. 

 Plants tufted: leaf-blades ascending. 12. E. nitirius. 



Spike la.\; spikelets distant: glumes glabrous. 13. E. Pelerscmii. 



Empty glumes linear-subulate. 



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



Spike 5 mm. thick: awns 5-10 mm. long. 15. E. Macoiinii. 



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

 Empty glumes strongly 3-5-nerved. 



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



16. E. curvaliis. 

 Empty glumes neither thickened nor strongl.v curved at the base, more or less 

 scarious-margined. 17. E. HoucUii. 



Empty glumes l-nerved or indistinctly 3-nerved. 

 I>emma glabrous or hispidulous 



Empty glumes aristiform or narrowly subulate. 



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



rous-hispidulous. 18. E. condensalus. 



Plant slender, 3-10 dm. liigh; 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. slrigosus. 



Spikelets usually singly; lemma acuminate or acute. 



22. E. saliniis. 

 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. cinereus, with horizontal rootstocks; 

 lemma not long-attenuate. 

 Lemma appressed-piibescent. 



Stem, sheath, and leaves glabrous or minutely strigulose. 



2.5. E. arenicoln. 

 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, scabrotis. 28. E. innovatus. 



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

 blades 1-3 dm. long, 4-10 mm. wide, scabrous; spike 5-15 cm. long, thick, erect; 

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

 N.S.— Fla.— Tex.— Sask. Plain. J^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; sj)ikelets usuall>' 

 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. Sanil 

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



3. E. diversiglumis Scribn. & 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. Jl. 



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; sj)ike 12-18 cm. long, 2.5- 1 

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



