GRASS FAMILY 41 



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

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

 ing or ascending. Styles distinct; stigmas plumose. 



Awns neither twisted nor bent. 



Panicle narrow; branches erect or ascending;. 

 First plume mucli shorter than the second. 



Spikelets not crowded, usually 1-3, on branches naked at the base; awn over 

 2 cm. long; perennials. 

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



lemma. 1. A. longiseta. 



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

 lemma. 2. A. Fendleriana. 



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

 base; awn less than 2 cm. long; annuals. 

 Stem 3-6 dm. high; first glume 7-8 mm. long; middle awn 10-16 mm. long; 



leaf-blades usiially flat. .3. A. fasciculate. 



Stem 1-3 dm. high; first glume 4-6 mm. long; middle awn 6-8 mm. long; 

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



First glume nearly equalling the second; perennials with a dense panicle. 



7. A. arizonica. 

 Panicle open; branches 3-forked, divergent. 5. A. Humboldtiana. 



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



1. A. longiseta Steud. Densely tufted glaucous glabrous peremiial; stem 

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

 2-11 cm. long; s{)ikelets purplish; first empty glume shorter than the lemma; 

 lemma 12-16 mm. long; awns 6-1 1 cm. long. Sandy soil: 111. — Tex. — -Ariz. — 

 Wash.; jNIex. I'l<nn — Subtnont. ]My-.4u. 



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 nun. long; central awn 2-3.5 cm. long; lateral awns a Httle shorter. 

 A. jjurpurta Coult., not Nutt. .4. loiu/iaela Fendleriana Merrill. Dry soil: 

 Tex. — Mont. — Calif. Son. — Plain — Subinonl. 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; fii-st glume 1-nerved, shorter than 

 the second; lemma equalling or longer than the second; awns ascending, the 

 lateral ones shorter than the middle one. (Mistaken for .4. oligantha 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.; ^lex. Son. .\p-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. diiaricala 

 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 Neb.— Okla. Aust. S-0. 



7. A. arizonica Vasey. 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, peduncled, the other shorter 

 and .sessile; glumes 12-14 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. — Suhniont. 



