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



4a. Lemma densely appressed-villous with white hairs 3 to 4 mm. long, rising above 

 the summit in a pappuslike crown. 

 Culms 1 to 2 m. tall; spikelets about 2 cm. long: awns 4 to 5 cm. long. 



5. S. COROXATA. 

 Culms not more than 50 cm. tall; spikelets less than 1 cm. long; awns about 2 cm. 



long 32. S. PLXETORUM. 



4b. Lemma often villous but the hairs not more than 1 mm. long, or sometimes those 

 at the summit as much as 2 mm. long. 

 5a. Summit of mature lemma smooth, cylindric, whitish, forming a ciliate crown 



0.5 to 1 mm. long (see also S. pulchra). 3. S. leucotricha. 



5b. Summit of mature lemma not forming a crown. 



6a. Lemma 2-lobed at summit, the lobes extending into awns 2 to 3 mm. long 



on each side of the central awn 4. S. stillmaxii. 



6b. Lemma not lobed at summit or only obscurely so. 



7a. Awn plumose below, the hairs ascending or spreading (compare *S. pulchra, 

 with appressed-hispid awn). 

 Awns once or obscurely twice-geniculate, hairs at summit of lemma longer. 



23. S. CURVIFOLIA. 

 Awns distinctly twice geniculate. 



Ligule 3 to 6 mm. long, hyaline 17. S. thurberiana. 



Ligule minute, mostly hany. 



Lemma 8 to 10 mm. long; glumes firm.. 19. S. latiglumis. 



Lemma 6 to 8 mm. long; glumes thin. 



Hairs on upper part of lemma longer than those below; culms 60 

 to 125 cm. tall. 



Sheaths pubescent 18. S. elmeri. 



Sheaths glabrous. 22. S. califorxica. 



Hairs short all over the lemma; culms 25 to 40 cm. tall. 



20. S. OCCIDEXTALIS. 



7b. Awn scabrous or nearly glabrous, rarely appressed-hispid, not plumose. 



8a. Lemma more than 7 mm. (often 1 to 2 cm.) long, glabrous or sparsely 



pubescent above the callus, mostl}' cylindric (somewhat fusiform in 



S. pulchra). 



Mature lemma pale or finally brownish, sparsely pubescent to summit, 



mostly more than 1 cm. long 10. S. comata. 



Mature lemma dark. 



Lemma 8 to 10 mm. long. 



Glumes 3-nerved; summit of lemma hispidulous-ciliate, the hairs 

 erect, nearh T 1 mm. long. 

 Lemma slender, cylindric; basal blades usually numerous, narrow, 



involute, glaucous, pilose 12. S. cerxua. 



Lemma fusiforme; blades green 11. S. pulchra. 



Glumes 5- to 9-nerved. 



Lemmas glabrous above the base, minutely roughened at apex; 



callus with fine sharp point.... 8. S. avexacea. 



Lemmas sparsely pubescent to apex; callus rather blunt. 



13. S. PRIXGLEI. 

 Lemma 12 to 25 mm. long, cylindric. 



Mature lemma glabrous above the callus 7. S. avexacioides. 



Mature lemma more or less pubescent above the callus. 



9. S. SPARTEA. 

 8b. Lemma less than 7 mm. long, or if as long as 7 to 8 mm., distinctly 

 pubescent on the upper part (see also S. cernua). 

 Panicle open, the branches spreading or ascending, naked at base. 

 Panicle diffuse, the branches divergent, drooping; lemma about 5 mm. 



long; awn about 2 cm. long 6. S. richardsoxi. 



Panicle open but not diffuse. 



Ligule 3 to 6 mm. long; awn about 5 cm. long, the terminal segment 



flexuous 14. S. EMIXEXS. 



Ligule 1 mm. long or less; awn 2.5 to 4 cm. long 15. S. lepida. 



Panicle narrow, the branches appressed. 



Hairs on lemma copious, at least at summit, 2 mm. long. 



Lemmas evenly villous all over; summit with lobes 0.8 to 1.5 mm. 



long 21. S. LOBATA. 



Lemmas conspicuously villous above, less so below; summit not 

 lobed or obscurely so. 

 Lemma about 8 mm. long, villous at summit, pubescent below. 



24. S. SCRIBXERI. 



