78 POACEAE 



21. P. subtrivialis Rydb. Perennial, with a rootstock; stem slender, 4-6 

 dm. high, smooth; leaf-blades erect, flaccid, 8-15 cm. long, about 2 mm. wide, 

 flat, dark green; panicle 1-2 dm. long; spikelets light green, 3-4 mm. long, 2-3- 

 flowered; lemma 2.5 mm. long, glabrous; cobweb very scant. Meadows: Wyo. 

 Ida. Mont. 



22. P. interior Rydb. Tufted perennial; stem slender, 3-6 dm. high; leaf- 

 blades 2-8 cm. long, about 2 mm. wide, glabrous; panicle 4-10 cm. long; spike- 

 lets 2-5-flowered, 3-5 mm. long; lemma 2-2.5 mm. long, scabrous on the mid- 

 nerve and lateral nerves. P. nemoralis Scribn., not L. Woods and copses: 

 S.D. Neb. N.M. Utah Wash. Alaska. Plain Mont. 



23. P. crocata Michx. Tufted perennial; stems strict, erect, 2-4 dm. high; 

 leaf-blades narrow, erect, 1-2 mm. wide, 4-10 cm. long, usually involute; panicle 

 rather narrow, 5-15 cm. long; spikelets 2-4-flowered, about 4 mm. long; lemma, 

 about as long as the glumes, pubescent on the midnerve and lateral nerves. P. 

 nemoralis strictior A. Gray. Dry hills and meadows: Lab. Vt. 'Minn. Colo. 

 Ariz. 'Alaska. Submont. -Subalp. Je-Au. 



24. P. alpina L. Stem 0.5-4 cm. high, erect or decumbent at the base; 

 ligules truncate; leaf-blades 2-8 cm. long, 2-4 mm. wide, abruptly acute, flat; 

 panicle 2-8 cm. long; spikelets 3-5-flowered, 5-6 mm. long; empty glumes broad, 

 glabrous, acute, scabrous on the keel; lemma about 4 mm. long, obtuse, its 

 lower half pubescent. Alpine-arctic regions in wet places: Greenl. Que. 

 Colo. Utah Alaska; Eu. Mont. -Alp. Je-Au. 



25. P. Olneyae Piper. Stem 3-8 dm. high, glabrous; blades of the basal 

 leaves 1-2 dm. long, often conduplicate, 2-3 mm. wide, those of the stem-leaves 

 3-6 cm. long, 2-3 mm. wide, flat; panicle pale green, about 1 dm. long, drooping,, 

 open; spikelets 7-10 mm. long, 4-6-flowered; lemma ovate, 5 mm. long. P. 

 Wheeleri Auth., not Vasey. Pine woods and meadows: Mont. Colo. Ore. 

 B.C. Submont. Subalp. Jl-Au. 



26. P. subreflexa Rydb. Stem ascending, 5-6 dm. tall; leaf-blades flat; 

 flaccid, 7-10 cm. long, 3-4 mm. wide, spreading; panicle open, about 1 dm. long,, 

 spikelets pale green, 6-7 mm. long, 3- or 4-flowered; lemma lanceolate, 5 mm. 

 long. Wooded banks: Colo. Mont. Subalp. Jl. 



27. P. Wheeleri Vasey. Stem simple, 2-6 dm. high; leaf -blades 2-20 cm. 

 long, 3 mm. wide, the lower involute or conduplicate; panicle open, 8-12 cm. 

 long; spikelets 6-7 mm. long, 3-5-flowered, light green, rarely tinged with purple; 

 lemma lanceolate, acute, 5 mm. long. Meadows: Alta. -Colo. Utah B.C. 

 Submont. Subalp. Jl-Au. 



28. P. Vaseyana Scribn. Stem 5-7 dm. high; leaf-blades flat, 5-30 cm. 

 long, 4-5 mm. broad; panicle open, 10-15 cm. long; spikelets often tinged with 

 purple, 4-6-flowered, 8-10 mm. long; lemma 5.5-6.5 mm. long. Mountain, 

 meadows: Colo. Wyo. Mont. Subalp. Au. 



29. P. tricholepis Rydb. Stem slender, 3-5 dm. high; leaf -blades 5-10 cm. 

 long, a little over 1 mm. wide, scabrous; stem-leaves 2-6 cm. long, sometimes 

 nearly 2 mm. wide; ligules lanceolate, acuminate; panicle 6-8 cm. long, open; 

 spikelets 3-4-flowered, 5-8 mm. long; lemma about 4 mm. long, green, bordered 

 with purple and a scarious border. Mountains: Colo. Mont. 'Alp. Jl-Au. 



30. P. Tracyi Vasey. Stem 3-8 dm. high; leaf-blades 6-12 cm. long, 2-6 

 mm. wide, scabrous; panicle 1-2 dm. long; spikelets 3-5-flowered, light green, 

 loose; lemma finely strigulose-scabrous, especially on the nerves, 4-5 mm. long. 

 P. occidentalis (Vasey) Rydb., not Vasey. Mountains: N.M. Colo. Utah. 

 Submont. -Subalp. Jl-Au. 



31. P. curta Rydb. Stem glabrous, 4-5 dm. high; leaf -blades 2-5 cm. long, 

 3-5 mm. wide, abruptly acute, dark green; inflorescence short, open, 4-5 cm. 

 long; spikelets light green, strongly compressed, about 6 mm. long, 2-4-flowered; 

 lemma lanceolate. Wooded banks: Wyo. Mont. Jl. 



32. P. Grayana Vasey. Stem 5-6 dm. high, leafy; ligules triangular- 

 lanceolate or ovate, acute; blades 1-2 dm. long, about 2 mm. wide; panicle 6-10 

 cm. long, open; spikelets 4-5-flowered, 6-7 mm. long; lemma lanceolate, green 



