76 POACEAE 



nearly 2 mm. long; lemma 2.5-3 mm. long, the nerves pilose below. Waste 

 places and cultivated ground: Lab. Ga. Calif. B.C.; Mex.; nat. from Eu. 

 Plain Mont. My-O. 



2. P. Bigelovii Vasey <fe Scribn. Annual, usually more or less tufted; 

 ligules lanceolate, 3 mm. long; leaf-blades flat, flaccid, 5-10 cm. long, 2-4 mm. 

 wide; panicle 5-15 cm. long, narrow; spikelets 4-6 mm. long, compressed; empty 

 glumes glabrous, lanceolate, acute, nearly as long as the lemma; lemma 3-4 mm. 

 long, subacute, villous on the midrib and marginal nerves; cobweb scant. Arid 

 regions: Tex. Colo. Utah Calif. L. Calif. Son. Submont. 



3. P. pratensis L. Stem 3-12 dm. high, smooth; leaf -blades 1-6 mm. wide, 

 those of the stem 5-15 cm. long, the basal ones longer; panicle 5-20 cm. long, 

 ovate or conical; spikelets 3-6-flowered, 4-5 mm. long; midvein and marginal 

 veins of the lemma silky below, the intermediate ones glabrous. Meadow's, 

 fields and woods: Greenl. Fla. Calif. Alaska; Eurasia. Plain Subalp. 

 Je-Au. 



4. P. rhizomata Hitchc. Perennial, with a creeping rootstock; stem 3-6 

 dm. high, smooth; sheaths smooth, the lower loose and papery; ligules 2-3 mm. 

 long; blades mostly flat, 1-2 mm. wide, 3-7 cm. long; panicle 3-5 cm. long; 

 spikelets 3-4-fl owered ; first glume 3 mm. long, the second 4 mm. long; lemma 

 5 mm. long, acutish, copiously webbed at the base; keel and marginal nerves 

 short-pilose below; internerves sparingly scabrous. Damp woods: Calif. Ida. 

 Ap-Je. 



5. P. occidentalis Vasey. Stem 3-10 dm. high; sheaths flattened, scab- 

 rous; leaf-blades 5-15 cm. long, flat, 2-6 mm. wide, scabrous; panicle large, 1.5-3 

 dm. long, loose; spikelets 2-4-flowered, 4-6 mm. long, light green; empty glumes 

 acute, scarious margined, unequal; lemma 3-4 mm. long, slightly pubescent 

 below and on the keel; cobweb scant. P. platyphylla Nash & Rydb. Rich 

 hillsicles: N.M. Colo. -Utah. Submont. Subalp. My-Au. 



6. P. callida Rydb. Stem 3-5 dm. high, somewhat flexuose; leaf-blades 

 flat, flaccid, 5-12 cm. long, about 3 mm. wide; panicle open, 1-1.5 dm. long; 

 spikelets about 3 mm. long, 2- or 3-flowered, light green; first empty glume sub- 

 ulate, 2 mm. long, the second slightly broader, 2.5 mm. long, glabrous; lemma 

 3 mm. long, glabrous except the keel, which is slightly silky below; cobweb scant 

 but long. Warm springs: Mont. Jl. 



7. P. lanata Scribn. & Merr. Perennial, with a creeping rootstock; stem 

 2.5-4 dm. high; sheath loose, the lower marcescent, scabrous; ligule 4 mm. long, 

 obtuse; blades 2-4 mm. wide, conduplicate or involute; inflorescence open; 

 branches in pairs, 2-3 cm. long, with 1-3 spikelets near the ends; spikelets 3-6- 

 flowered; lemma purple, 6-7 mm. long. Subarctic situations: Alaska B.C. 

 Subarct. 



8. P. cenisia All. Stem 1-3 dm. high, slender; ligules 1-2 mm. long, trun- 

 cate; blades 2-10 cm. long, 1-2 mm. wide, involute; panicle 2-8 cm. long, open; 

 spikelets 2-4-flowered, 5-6 mm. long, purplish; empty glumes glabrous; lemma 

 about 4 mm. long. Arctic-alpine situations: Greenl. Lab. Colo. Alaska; 

 Eu. Alp. Jl-Au. 



9. P. arctica R. Br. Stems 1-3 dm. high, smooth, erect or decumbent at 

 the base; ligules erose-truncate; basal leaf-blades 5-10 cm. long, 2-4 mm. wide; 

 stem-leaves shorter and often flat; panicle open, 5-10 cm. long; spikelets purple; 

 empty glumes 3-3.5 mm. long, glabrous; lemma 4 mm. long, acute. Alpine- 

 arctic situations: Arctic Sea N.M. Utah. Alp. Jl-Au. 



10. P. longipila Nash. Stem 3-5 dm. high; ligules broad, obtuse or acut- 

 ish; leaf-blades erect, acuminate, 3-8 cm. long, 3-4 mm. wide, flat; panicle 6-9 

 cm. long; spikelets 6-8 mm. long, 3-4-flowered, purple; lemma 5-6 mm. long; 

 cobweb copious and long. Wet places: Wyo. Mont. Submont. 



11. P. callichroa Rydb. Perennial, with a horizontal rootstock, but more 

 or less matted; stem about 3 dm. high; blades of the lower leaves 6-10 cm. long, 

 firm, dark-green, strongly veined; blades of the upper leaves about 3 cm. long. 



