GRASS FAMILY 41 



rigid, strongly convolute, with a prominent callus at the base, 3-a\vned at the 

 apex; the central awn often bent and twisted, the lateral ones shorter and spread- 

 ing or ascending. St^'les distinct; stigmas plumose. 



Awns neither twisted nor bent. 



Panicle narrow; branches erect or ascending. 

 First glume much shorter than the j^econd, 



Spikelets not crowded. usuaUy 1-3. on branches naked at the base; awn over 



2 cm. long; pereiuiials. 

 Second glume of the spikelets 2 cm. long or more. 1.5-2 times as long as the 



lemma. 1. a, Ivngiseta. 



Second glume of the spikelets 1.5 cm. long or less, scarcely exccedhig the- 

 lemma. , , , 2. A, Fcndleriana. 



Spikelets crowded. 4-6 on the short branches, spikelet-bearing to near the- 



base; aw^l less than 2 cm. long: annuals. 

 Stem 3-6 dm. high; first glume 7-8 mm. long; middle awn 10-10 mm. long; 



leaf-blades usually flat. 3. -V, fasciculata. 



Stem 1-3 dm. high; first glume 4-6 mm. long; middle awn 0-S mm. long: 

 leaf-blades strongly involute. 4. A. bromoides. 



rivisi glume nearly equalling tlie second; perennials witii a dense panicle. 



i.f f,^"^^'^ open; branchejS-forked. divergent. 5. A. IlumboUiiiana, 



Middle awn twisted and divaricately bent near the base. 6. A. CuriUsii. 



1. A. longiseta Steud. Densely tufted glaucous glabrous perennial; stern 

 1-4 dm. high; sheaths shorter than the internodes; leaf-blades strongly involute^ 

 2-11 cm. long; spikelets purplish; first empty glume shorter than the lemma; 

 lemma 12-16 mm. long; awns 6-11 cm. long. Sandy soil: 111.— Tex.— Ariz.— 

 Wash.; Mex. Plain— Sub mont. IMy-Au, 



2. A, Fendleriana Steud. Densely tufted glabrous perennial; stem 1.5-3 

 dm. high, erect; sheaths smooth, confined to the base of the stem; leaf-blades 

 involute, often curved; panicle 7-10 cm. long, strict; spikelets 12-15 mm. long; 

 lemma 9-12 mm. long; central avm 2-8.5 cm. long; lateral awns a little shorter. 

 A. purpurea Coult., not Xutt. A, longiseta Fendleriana Merrill. Drv soil: 

 Tex.— Mont.— Calif. Son.— Plain — SubmonL Je-S. 



3. A. fasciculata Torr. A tufted annual; stems 3-6 dm. high, branched; 

 leaf-blades 5-15 cm. long, 2 mm. wide; panicle 5-17 cm. long, loose; branches 

 at first strict, later more or less spreading; first glume 1-nerved, shorter than 

 the second; lemma equalling or longer than the second; a^ras ascending, the 

 lateral ones shorter than the middle one. Qlistaken for .-I. oliganiha Michx.) 

 Dry soil: Tex. — ^Kans.— s Utah— Ariz.— Mex. Son. My-S. 



4. A. bromoides H.B.K. Low tufted annual; stem 1-3 dm. high; leaf- 

 blades 2-7 cm. long, involute; panicle purple, 2-5 cm. long, dense; first glume 

 one-nerved, shorter than the second, slightly longer than the lemma; awns 

 ascending, 'the lateral ones 6-8 mm. long. Arid regions: Tex.— Colo.— Utah- 

 Calif.; Mex. Son, Ap-N. 



5. A. Humboldtiana Trin. & Rup. Tufted perennial; stem 3-9 dm. high^ 

 branched; sheaths rough; blades of the stem-leaves 1.5-3 dm. long, 2-4 mm. 

 wide; those of the sterile shoots longer and narrower; panicles 3-5 dm. long, 

 open; empty glumes acuminate, awn-pointed, 9-13 mm. long; central awn 1.2-2 

 cm. long, erect; lateral ones somewhat shorter, ascending. ^4. divaricaia 

 H.B.K. Dry soil: Kans. — Colo. — Ariz.; Mex. Son. Jl-S, 



6. A. Curtissii (A. Gray) Nash. Tufted; stem 2-5 dm. high, branching;, 

 leaf -blades 4-16 cm. long, 1-2 mm. wide; panicle spike-like, 5-9 cm. long, branches 

 short, erect; first glume shorter than the second, which usually equals the lemma,, 

 7-11 mm. long; middle awn 10-15 mm. long; lateral awns 1-2 mm. long, straight. 

 Dry soil: Va. — w Xeb. — Okla. Aust, S-0. 



7. A. arizonica Va^ey. Tufted perennial; stem 3-6 dm. high, rigid, glab- 

 rous; leaf-blades 1-2 dm. long, becoming involute: panicle 1-2.5 dm. long; 

 branches 2 at each node, appressed, one longer, peduneled, the other shorter 

 and sessile; glumes 12-U mm. long, bidentate at the apex; awns of the lemma 

 nearly equal, 1.5-2 cm. long, divergent when mature. Plains and hills: Tex 

 s Colo. — Utah — Ariz. Son. — Suhmont. 



