GRASS FAMILY 93 



Spikolels compresseci, spreading. 5. A. arizonicum. 



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

 lanceolate, acuminate. 

 Sheaths conspicuously i)ilose. 16. A. Palmcri. 



Sheatlis t^'lahrous or nearly so. 



Lenuna 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. moUe. 



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. subvillosum. 

 Lemma long-villous. 23. A. dasystachyum. 



1. A. Scribneri \'asey. Densely tufted perennial; stems decumbent and 

 geniculate at the base, 2-5 dm. high; leaf-blades short, 3-10 cm. long, 2-4 mm. 

 wide, rigid, attenuate-pointed; spike 5-7 cm. long, fle.xuous; spikelets 3-6- 

 flowered; empty glumes linear-lanceolate or subulate, 3-5-nerved, smooth, long- 

 awned; lemma oblong-lanceolate, 8-10 mm. long, smooth, 5-nerved; a-mi diverg- 

 ent, scabrous, 1.5-2.5 cm. long. This species connects the genus with Silanion. 

 High moimtains; Mont. — N.M. — Ariz. Siibalp. — Alp. Jl-Au. 



2. A. Gmelini (Griseb.) Scribn. & Smith. Stems 6-12 dm. high, glabrous, 

 slender; blades of stem-leaves 12-30 cm. long, fiat or involute; those of the basal 

 leaves 3-7 cm. long, 4-6 mm. wide; spike slender, 1-2.5 dm. long; spikelets 10- 

 20, 6-9 mm. long, 7-9-fiowered ; empty glumes unequal, 10-14 mm. long, oblong- 

 lanceolate, acimiinate or short-awned; lemma oblong-lanceolate, acuminate, 

 10-12 mm. long; awn scabrous, 15-30 mm. long, at last divergent. Hillsides: 

 Wash. — -Alta. — Wyo.; Siberia. Submont. Jl-Au. 



3. A. Vaseyi Scribn. A: Smith. Stem erect, 3-5 dm. high, wiry, glabrous; 

 leaf-blades 3-15 cm. long, 1-2 mm. wide, usually involute; spike slender, 5-10 

 cm. long, often somewhat flexuose; spikelets 3-5-flowered ; empty glumes oblance- 

 olate or oblong, acute or acimiinate, 6-8 mm. long; lemma 8 mm. long, lanceo- 

 late, acute; awn 8-10 mm. long. Hills and mountain sides: Wash. — Ore. — 

 Colo.— Mont, Suhmo?}t. My-Au. 



4. A. spicatum (Pursh) Scribn. t\: Smith. Stem 3-10 dm. high, glabrous; 

 leaf-blades 5-20 cm. long, 1-2 mm. wide, involute or rarely flat; spikes 8-20 cm. 

 long; spikelets 3-6-flowered, flattened; lemma 8-10 mm. long, scabrous above; 

 awii stout, 12-25 mm. long. A. divergens Nees. Bunch Grass. Dry rocky 

 hills and bench-lands: B.C. — Calif. — Ariz. — Colo. — Mont. Plain — Subinoti't. 

 Je-Au, 



5. A. arizonicum Sciilni. & Smith. Tufted, but occasionally with long 

 stolons; stem 4-6 dm. high, minutely scabrous below; leaf-blades 1-3.5 dm. 

 long, 4-6 mm, wide; spike 7-20 cm, long, usually nodding; spikelets 7-14, distant, 

 5-7-flowered, 2-3.5 cm. long, 3-5-nerved; lemma 10-15 mm. long, acuminate, 

 scabrous; awn about 2.5 mm. long. Mountains: Colo. — N.M. — Ariz.;nMex. 

 Submo7ii.. — Subalp. Au-0. 



6. A. Bakeri E. Nels. Stem smooth, 3-5 dm, high; leaf-blades rigid, flat, 

 1-3 dm. long, 2-4 mm. wide; spike 9-12 cm, long, dense, scarce!}' exserted; 

 spikelets about 5-flowered, 15-19 mm, long; empty glumes 11-12 mm. long, 

 scarious-margined, abruptly acimiinate, short awned; lemma scabrous or nearly 

 smooth, about 12 mm, long, attenuate; awn 1-3.5 cm. long. High mountains: 

 Colo.— N.M. Mont. Au. 



7. A. Richardsoni (Trin.) Schrad. Stems smooth, 6-8 dm, high; leaf- 

 blades 8-20 cm. long, 2-6 mm. wide, scabrous, flat, often with involute tips; 

 spikes 7-10 cm. long, one-sided; spikelets 3-4-flowered; empty glume 12-16 mm. 



