54 POACEAE 



2. A. atrata Rydb. A somewhat tufted perennial; stems 1.5-3 dm. high, 

 few-leaved, more or less bulbous at the base; leaf-blades 5-10 cm. long, about 2 

 mm. wide, flat, smooth; panicle 5-8 cm. long; empty glumes nearly equal; 

 lemma nearly as long, obtusish. Mountains: B.C. Mont. Subalp. 



3. A. Thurberiana Hitchc. Tufted perennial; stem 2-4 dm. high, 

 leafy; leaf -blades 5-10 cm. long, 2 mm. wide, lax, light green; panicle more or 

 less drooping, 5-20 cm. long; empty glumes about 2 mm. long, narrow, gradually 

 acute; lemma nearly as long, obtuse, faintly 5-nerved. Meadows: B.C. Mont. 



-Utah -Calif. Submont. -Subalp. Jl-Au. 



4. A. stolonifera L. Perennial, with a long creeping rootstock and stolons; 

 stem 2-8 dm. high; leaf-blades 5-10 cm. long, 3-4 mm. wide, light- or glaucous- 

 green, scabrous; panicle interrupted, 3-10 cm. long; empty glumes obtuse, 

 scabrous on the keel and back, 2 mm. long; lemma about half as long, awnless, 

 truncate and toothed at the apex. A. verticillata Vill. Wet meadows: Tex. 

 Utah Calif.; Mex., C. Am., S. Am., Eu., Africa and Asia. Son. Submont. F-O. 



5. A. alba L. Tufted perennial; stems 2-15 dm. high, erect or decumbent 

 at the base; leaf-blades 4-15 cm. long, 3-8 mm. wide; panicle upright, 5-30 cm. 

 long, with spreading branches, the lower usually verticillate; empty glumes 2-3 

 mm. long, pale or purplish, nearly equal, acute; lemma two-thirds to three- 

 fourths as long, obtuse, seldom awned. Wet meadows: Newf. Fla. Calif. 

 B.C.; Eurasia. Plain Submont. Je-O. 



6. A. humilis Vasey. Tufted perennial; stems 1-4 dm. high, slender, 1-3- 

 leaved; leaves mostly basal; leaf-blades 2-10 cm. long, 1 mm. wide or less, usually 

 conduplicate; panicles 2-5 cm. long; branches ascending; empty glumes equal, 

 abruptly pointed, 1.5-2 mm. long, purple; lemma nearly as long, awnless. High 

 mountains: B.C. Ore. Colo. Wyo. Mont. Alp. Au-O. 



7. A. depressa Vasey. Tufted perennial; stems decumbent and geniculate 

 at the base, 1.5-2.5 dm. high, slender, leafy below; leaf-blades 3-5 cm. long, 1 

 mm. wide, flat; panicle narrow, 3-5 cm. long, in age open; empty glumes 2 mm. 

 long, acute; lemma obtuse or minutely dentate at the apex. Mountains: Colo. 

 Mont. Subalp. Jl. 



8. A. reptans Rydb. Cespitose and stoloniferous perennial; stems 2-3 dm. 

 long; leaves 2-6 cm. long, 1-2 mm. wide, flat; panicle 3-5 cm. long; branches 

 ascending, flower-bearing to near the base; empty glumes purplish, nearly equal, 

 acute; lemma one-third shorter, toothed at the apex, often with a minute awn. 

 A. exarata stolonifera Vasey. Bottom lands: B.C. Calif. Submont. Jl-Au. 



9. A. foliosa Vasey. Perennial, with a creeping rootstock; stem 5-10 dm 4 

 high; leaf-blades 8-15 cm. long, 3-4 mm. wide; panicles open, but often narrow 

 1-1.5 dm. long; branches ascending, naked below; empty glumes pale, nearly 

 equal, 2-3 mm. long, abruptly acute; lemma nearly as long, obtuse and minutely 

 toothed at the apex, awnless or short-awned. Wet meadows: B.C. Ida. 

 Calif. Submont. Je-Au. 



10. A. grandis Trin. Tufted perennial; stem 5-15 dm. high; leaf-blades 

 1-2 dm. long, 6-10 mm. wide, very scabrous, abruptly contracted at the ligules; 

 panicle 1-2 dm. long, dense, contracted; empty glumes about 3 mm. long, grad- 

 ually tapering at the apex, light green, scarious-margined; lemma one-half to 

 two-thirds as long, obtuse. Wet meadows: B.C. Mont. -Neb. N.M. 

 Calif. Plain Mont. Je-Jl. 



11. A. asperifolia Trin. Tufted perennial; stem 3-6 dm. high; blades 5-15 

 cm. long, 2-5 mm. wide, scabrous; panicle 5-10 cm. long, narrow and dense; 

 empty glumes broadly lanceolate, 2.5-3 mm. long, usually abruptly pointed, 

 often tinged with purple; lemma two-thirds to three-fourths as long, awnless; 

 A. exarata minor Hook. A. Drummondii Torr. Wet meadows: Man. Neb. 

 N.M. Calif. B.C. Plain Mont. Je-Au. 



12. A. Rossae Vasey. Cespitose perennial; stem about 1.5 dm. high, smooth, 

 erect; leaf-blades 2-4 cm. long, flat, 2 mm. wide; panicle oblong, 2-4 cm. long, 

 dense; branches nearly erect, 1-2 cm. long, very scabrous; empty glumes 2 mm. 



