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



to be of value as soil or sand binders. E. mollis is a natural sea dune 

 grass and E. arenicola and E. flavescens are common on inland shifting 

 dunes; E. triticoides is to be recommended for holding embankments. 

 On the western ranges E. condensatus and E. triticoides are important, 

 la. Plants annual; spike long-awned, nearly as broad as long. 



I. E. CAPUT-MEDUSAE. 



lb. Plants perennial; spike much longer than broad. 

 2a. Rhizomes present, slender, creeping. 



Glumes lanceolate, awnless or awn-pointed. Plants of coastal dunes. 



Glumes and lemmas papery, distinctly nerved 2. E. MOLLIS. 



Glumes and lemmas firm, faintly nerved (lemmas nerved at apex) . 



3. E. VANCOUVERENSIS. 



Glumes subulate or very narrow. 



Spikelets glabrous; lemmas short-awned 8. E. TRITICOIDES. 



Spikelets densely villous to coarsely, sometimes sparsely, pubescent. 

 Lemmas awned or awn-tipped; spike 5 to 15 cm long. 



Lemmas copiously villous; awn 1 to 4 mm long__ 6. E. INNOVATUS. 

 Lemmas hirsute or hirtellous; awn 5 to 10 mm long. 



7. E. HIRTIFLORUS. 



Lemmas awnless; spike 10 to 25 cm long. 



Glumes pubescent; lemmas soft, densely villous 4. E. FLAVESCENS. 



Glumes glabrous or nearly so; lemmas relatively firm, coarsely 



pubescent, sometimes sparsely so 5. E. ARENICOLA. 



2b. Rhizomes wanting (or short and stout in E. condensatus}. Plants tufted. 

 3a. Rachis tardily disjointing. Glumes and lemmas awned. 



Spike mostly 5 to 7 mm wide; spikelets mostly in twos; blades subin volute. 



15. E. MACOUNII. 



Spike 8 to 10 mm wide; spikelets often in threes; blades flat, 5 to 10 mm wide. 



16. E. ARISTATUS. 

 3b. Rachis continuous. 



4a. Glumes subulate to subsetacepus, not broadened above the base, the 



nerves obscure except in E. villosus. 

 Lemmas awnless or awn-tipped, the awn shorter than the body. 



Spike thick, sometimes compound; spikelets commonly in twos to fours. 



II. E. CONDENSATUS. 



Spike slender; some or most of the spikelets solitary at the nodes, the 



paired spikelets near the middle. 

 Culms numerous in a close tuft, the leaves mostly basal; lemmas 



mostly awnless 10. E. SALINA. 



Culms few, loosely tufted, the leaves scattered along the usually 

 taller culms; lemmas awn-tipped, the awn 2 to 5 mm long. 



9. E. AMBIGUUS. 

 Lemmas awned, the awn as long as the body or longer. 



Awns straight; lemmas about 1.2 mm wide across the back. 



17. E. VILLOSDS. 

 Awns flexuous-divergent; lemmas about 2 mm wide across the back. 



18. E. INTERRUPTUS. 



4b. Glumes lanceolate or narrower, broadened above the base, strongly 



3- to several-nerved. 



Glumes relatively thin, flat, several-nerved, not indurate at base. 

 Lemmas sparsely long-hirsute on the margins toward the summit. 



14. E. HIRSUTUS. 

 Lemmas glabrous or scabrous. 



Lemmas awned 12. E. GLAUCUS. 



Lemmas awnless or minutely awn-tipped 13. E. VIRESCENS. 



Glumes firm, indurate at base. 



Awns divergently curved when dry; base of glumes not terete. 



19. E. CANADENSIS. 



Awns straight; base of glumes terete. 



Glumes about 1 mm wide about the middle, the bases not bowed out. 



20. E. RIPARIUS. 

 Glumes 1.5 to 2 mm wide about the middle, the bases bowed out. 



21. E. VIRGINICUS 



1. Elymus cap lit- medusae L. (Fig. 478.) Annual; culms ascend- 

 ing from a decumbent ; branching base, slender, 20 to 60 cm tall; blades 



