GRASS FAMILY 83 







Plant stout; branches of the inflorescence spreading or reflexed, not nodding. 



2. P. elata. 



Leaf-blades conduplicate, stiff, ascending; lemma distinctly scarious-mar- 

 gined; branches of the inflorescence short, strongly ascending, not droop- 

 ing. 3. P rigida. 

 Spikelets 4-6 mm. long; lemma narrowly oval, 2-3 mm. long; inflorescence ample; 



branches finally spreading. 

 Lemma barely scarious-margined ; empty glumes acute, lanceolate. 



4. P. grandis. 

 Lemma with broad scarious margins; empty glumes obtuse. 



5. P. pulchella. 

 Lemma 5-nerved, distinctly dentate at the apex, broadly scarious-margined. 



Spikelets 4-6-flowered. 6. P. pauciflora. 



Spikelets 2-flowered. 7. P. Holmii. 



Spikelets linear, 10 mm. long or more; lemma 7-nerved, erose. 



Spikelets 10-17 mm. lone, on pedicels at least one-third their length. 



8. P. borealis. 

 Spike'lets 15-20 mm. long, subsessile or nearly so. 9. P. septentrionalis. 



1. P. nervata (Willd.) Kimtze. Stem slender, 3-10 dm. high; leaf-blades 

 1.5-3 dm. long, 4-10 mm. wide, smooth beneath, scabrous above; panicle 7-20 

 cm. long, open; spikelets 3-7-flowered, 2-3 mm. long; lemma 1.5 mm. long, obtuse 

 or rounded at the apex, striate. Wet meadows and swamps: Lab. Fla. 

 Calif. Alaska; Mex. Submont. -Mont. Je-Au. 



2. P. elata Nash. Stem 5-15 dm. high, smooth; leaf -blades flat, scabrous 

 on both sides, 2-4 dm. long, 6-10 mm. wide; panicle ample, 2-3 dm. long; spike- 

 lets 3-4 mm. long, ovate, 4 7-flowered; empty glumes hyaline, 1-1.5 mm. long; 

 lemma 2 mm. long, its nerves vanishing near the apex. Shaded bogs: Mont. 

 Wyo. Calif. B.C. Submont. Mont. Jl-S. 



3. P. rigida (Nash.) Rydb. Stem 3-4 dm. high; leaf -blades 5-15 cm. long, 

 3-4 mm. wide; inflorescence small, about 1 dm. long; spikelets about 3 mm. long, 

 5-6-flowered; empty glumes about 1 mm. long, purplish; lemma rounded-oval, 

 usually purplish, about 1.5 mm. long. Bogs and springs: Mont. Ida. Wyo. 

 My-Jl. 



4. P. grandis (S. Wats.) Nash. Stem stout, 1-2 m. high, smooth; leaf- 

 blades 1.5-4 dm. long, 6-15 mm. wide, smooth beneath, scabrous above; panicle 

 2-4 dm. long, open; spikelets 4-7-flowered; lemma 2-2.5 mm. long. P. americana 

 (Torr.) McMill. In water and wet places: N.B. N.Y. N.M. Calif- 

 Alaska. Plain Submont. Je-Au. 



5. P. pulchella Nash. Stem 4-6 dm. high, stout, smooth; leaf-blades 1.5-3 

 dm. long, 2.5-6 mm. wide, flat; panicle open, 1.5-3 dm. long; spikelets 4-6- 

 flowered; empty glumes brownish or purplish, scarious-margined, obtuse; lemma 

 usually purple, scabrous, about 3 mm. long. Swamps: Yukon Mack. N.M. 

 Submont. Subalp. Jl-S. 



6. P. pauciflora (Presl.) Kuntze. Stem 3-10 dm. high; leaf-blades 1-3 dm. 

 long, 6-10 mm. wide, scabrous on both sides; panicle 1.5-2 dm. long, loose; 

 branches ascending or spreading; spikelets 4-5 mm. long; empty glumes 1 mm. 

 long, rounded at the apex; lemma about 3 mm. long, scabrous. Wet meadows 

 and in water: Mont. -Colo. Calif. B.C. Submont. Subalp. Jl-Au. 



7. P. Holmii Beal. Stem 2.5-5 dm. high, pale; leaf-blades flat, 4-12 cm. 

 long, 4-7 mm. wide, scabrous; panicle open, lax, 5-8 cm. long; empty glumes 

 hyaline, 1-1.3 mm. long; lemma scabrous, 2-2.2 mm. long. Shaded streams: 

 Colo. Mont. Jl. 



8. P. borealis Nash. Stem glabrous, 6-15 dm. high; leaf-blades 1-2 dm, 

 long, 2-10 mm. wide, erect, scabrous on both sides; panicle narrow, 2-5 dm. long; 

 branches erect, smooth; spikelets 7-13-flowered; empty glumes scarious-mar- 

 gined, 1-nerved, the first acute, the second obtuse, erose; lemma 3.5-4 mm. 

 long. Water and wet places: Me. N.Y. -N.M. Calif. Alaska. Submont. - 

 Mont. Jl-Au. 



9. P. septentrionalis Hitchc. Stem 1-1.5 m. high; blades 1-2.5 dm. long, 

 6-8 mm. wide; panicle 2-2.5 dm. long, subflexuose; spikelets 8-12-flowered; 

 empty glumes obtuse; lemma 4-4.5 mm. long, hispidulous. Glyceria fluitans 

 Am. 'auth., not R. Br. Shallow water: Newf. Va. Calif. B.C. Plain- 

 Submont. 



