38 POACEAE 



Lemma with a long, more or less divergent awn. 



Lemma pubescent. 14. A. albicans. 



Lemma glabrous or scabrous. 



Spikelets subterete, appressed. 15. A. Griffithsii. 



Spikelets compressed, spreading. 5. A. arizonicum 



Lemma awnless or with a very short erect awn; empty glumes usually narrowly 

 lanceolate, acuminate. 

 Sheaths conspicuously pilose. 16. A. Palmcri. 



Sheaths glabrous or nearly so. 



Lemma glabrous or merely scabrous. 



Spikelets erect, nearly cylindric or slightly compressed. 



Spike elongate; empty glumes nearly equalling the spikelets. 



17. A. pseudorppens. 

 Spike short; empty glumes about half as long as the spikelets. 



18. A. riparium. 

 Spikelets much flattened, spreading. 19. A. Smithii. 



Lemma from villous to hispidulous. 

 Lemma short-pubescent. 



Spikelets compressed, more or less spreading; lemma acuminate or 



strongly acute. 20. A. molle. 



Spikelets terete or nearly so, erect; lemma obtuse or acutish. 

 Spike loose, elongate; lemma sparingly pubescent. 



21. A. lanceolatum. 

 Spike dense and short; lemma densely pubescent. 



22. A. subvillosuni. 

 Lemma long-villous. 23. A. dasystachyitm. 



73. TRITICUM L. Wheat. 



Empty glumes distinctl.v keeled only at the apex; grain dull, neither glossy nor semi- 

 translucent. 1. T. aestirum 



Empty glumes distinctly keeled, almost winged, to the base; grain glossy, often some- 

 what translucent. 2. T. durum. 



74. SECALE L. Rye. i. s. cena'c 



75. HORDEUM L. Barley, Squirrel-tail, Foxtail. 



Lateral snikelets sessile; annuals. 



Lemma not awned, the awns represented by chartaceous lobes. 1 . H. acgiceras. 



Lemma awned. 2. H. vulgare. 



Lateral spikelets .stalked; lemma awned. 

 Floret of the central spikelet sessUe. 



Empty glumes of the central spikelets lanceolate. 3. H. pusilluni. 



Empty glumes of central spikelet not lanceolate. 



Inner empty glumes of ttie lateral spikelets broadened. 4. //. marilimum. 



Empty glumes all setaceous. 

 Lateral floret not awned. 



Plant low, 5-25 cm. loigh; upper sheaths inflated. 5. H. depressum. 

 Plant taller, 2-6 dm. high; upper sheath not conspicuously inflated. 

 Lateral floret neutral or staminate; lemma of the central floret 6-8 



nim. long. 6. H. nodosum. 



Lateral floret usually perfect; lemma of the central flower 10 mm. 

 long. 7. //. boreale. 



Lateral florets long-awned. 



Awn 2-3 cm. long. 8. H. caespitosum. 



Awn 4-6 cm. long. 9. H. jubatum. 



Floret of the central spikelets stalked. 



Empty glumes not ciliate. 10. H. montanense. 



Empty glumes or some of them ciliate. 11. H. murinum. 



76. SITANION Raf. 



Empty glumes lanceolate, scarious-margined. 



Leaf-blades not wliite-margined. 1. S. lanceolalum. 



Leaf-blades white-margined. 2. 5. marqinatum. 



Empty glumes setaceous, or cleft into setaceous divisions, not scarious-margined. 

 Empty glumes setaceous, entire; lowesl flower perfect. 



Lemma soft^pubescent. 3. S. pubiflorum. 



Lemma glabrous. 4. S. elymoides. 



Empty glumes or some of them 2-cleft; lowest flower rudimentary. 

 Lemma pubescent; sheatlis and blades densely pubescent. 

 Blades and sheatlis short-hairy, subvelutinous. 



Awns at least 4 times as long as the lemma. 5. S. Ihjstrix. 



Awns 2-3 times as long as the lemma. 6. S. cinereum. 



Blades and sheatlis long-hairy. 7. S. ciliatum. 



Lemma glabrous or scabrous. 



Empty glumes subulate-lanceolate, bifid about two-thirds their length. 



8. S. insulare. 

 Empty glumes setaceous, or cleft to near the base into setaceous divisions. 

 Sheaths and blades more or less long-pubescent. 



Lemma glabrous. 9. S. molle. 



Lemma scabrous. 10. S. strigosum. 



Sheaths and blades glabrous, scabrous, or puberulent; lemma smooth 

 below, scabrous above. 



