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. Grifflthsii. 



Splkelets compressed, spreading. S. A. arizonicum. 



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

 lanceolate, acuminate. 

 Sheaths conspicuously pilose. 16. A. Palmeri. 



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. pseudorepens. 

 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 spaiingly pubescent. 



21. A. lanceolatum. 

 Spike dense and short; lemma densely pubescent. 



22. A. subvillosum. 

 Lemma loug-villous. 23. A. dasystachyum. 



73. TRITICUM L. Wheat. 



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

 translucent. 1. T. aestivum. 



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

 what translucent. 2. T. durum. 



74. SECALE L. Rye. l. S. cercale. 



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



Lateral spikelets sessile; annuals. 



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



Lemma awned. 2. H. vulgare. 



Lateral spikelets stalked ; lemma awned. 

 Floret of the central spikelet sessile. 



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



Empty glimaes of central spikelet not lanceolate. 



Inner empty glumes of the lateral spikelets broadened. 4. H. marilimum. 



Empty glumes all setaceous. 

 Lateral floret not awned. 



Plant low, 5—25 cm. high; 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 



mm. long. 6. H. nodosum. 



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

 long. 7. H. boreale. 



Lateral florets long-awned. 



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



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



Floret of the central spikelets stalked. 



Empty glumes not cUiate. 10. H. monlanense. 



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



76. SITANION Raf. 



Empty glumes lanceolate, scarlous-margined. 



Leaf-blades not white-margined. 1. S. lanceolatum. 



Leaf-blades white-margined. 2. S. marginatum. 



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

 Empty glumes setaceous, entire; lowest 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: sheaths and blades densely pubescent. 

 Blades and sheaths short-hairy, subvelutinous. 



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



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



Blades and sheaths long-hairy. 7. s. ciliatum. 



Lenuna glabrous or scabrous. 



Empty glumes subulate-lanceolate, bifld 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 pubenilent; lemma smooth 

 below, scabrous above. 



