GRASS FAMILY 39 



Awns of the lemma 3-4 cm. long, divergent; plant very low. 



11. S. rigidum. 

 \vrns of the lemma 4-7 cm. long; plant taller, more than 2 dm. high. 

 Leaf-blades 2-5 mm. broad, flat or slightly involute. 



Plant perfectly glabrous; awn ascending. 12. S. glabrum. 

 Plant puberulent or scabrous; awns divergent. 1,3. S. montanum. 

 Leaf-blades 1-2 mm. broad, strongly involute. 14. S. basalticola. 



77. ELYMUS L. Lyme-grass, Wild Rye, Rye-grass, Bufralo Rye. 



Lemma long-awned. 



Spike broad; splkelets spreading. 



Empt} glumes lanceolate to lanceolate-subulate; spike dense. 



Empty glumes lanceolate, 5-7-nerved, thick and strongly curved at the base; 

 spike erect. 

 Plant robust; spike scarcely exserted; lemma glabrous or nearly so. 



1. E. virginicus. 

 PlE^nt slender; spike long-exserted; lemma scabrous-hispidulous. 



2. E. jejunus. 

 Empty glumes narrowly linear-lanceolate, neither conspicuously thickened 



nor curved at the base; spike often nodding. 

 Empty glumes usually minute, less than 15 mm. long. 4. E. diversiglumis. 

 Empty glumes 15-30 mm. long. 



Lemma hirsute or villous. 3. E. canadensis. 



Lemma hispidulous-scabrous to glabrous. 



Bobust; spike usually included at the base; leaf-blades 8-15 mm. 



wide. 5. E. robustus. 



Slender; spike long-exserted; leaf-blades seldom more than 5 mm. 

 wide. 6. E. brachystachys. 



Empty glumes setaceous, hirsute; lemma hirsute; spike laxer. 7. B. slriatus. 

 Spike narrow; spikelets erect, appressed. 

 Lemma pubescent. 



Empty glumes lanceolate, 5-nerved. 8. E. vulpinus. 



Empty glumes lance-subulate, indistinctly veined. 9. E. angustus. 



Lemma scabrous or glabrous. 



Empty glumes lanceolate, acuminate or shorfc-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. marginalis. 

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



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



Empty glumes linear-subulate. 



Spike 7-8 mm. thick; awns 30-40 mm. long. 14. JE. SaundersU. 



Spike 5 mm. 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 strongly 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 ghimes 1-nerved or indistinctly 3-nerved. 

 t>emma 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. Irilicoides. 

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

 Spikelets usually in' pairs; lemma awn-pointed. 



T.a nriTn a. glabrous. 20. E. ombiguus. 



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. villiflorus. 



Plants not tufted, or somewhat so in E. cinereus, 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-viUous. 27. E. flavescens. 

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



78. HYSTRIX Moench. i. H. Hystrix. 



