poa GRAMINE^ 761 



P. gracillima Vasey Contrib. U. S. Nat. Herb, i, 272. A densely 

 tufted perennial: stems slender, 15-25 inches high, erect, smooth: sheaths 

 shorter than the internodes, smooth : ligules about 2 lines long, lanceolate, 

 acute: leaves of sterile shoots thin, smooth, acute, flat or conduplicate, 

 filiform, 2-5 inches long, *4r% hne wide, those of the stem 2, the upper 

 with very long sheath and short blade : panicle open, pyramidal or ovoid, 

 2-4 inches long, its scabrous branches in twos to fives, the longest 2-23^ 

 inches long, bearing 2-4 spikelets on the outer third : spikelets oval or ovate- 

 lanceolate, 3-5-flowered, 4-6 lines long: empty glumes lanceolate, acute, 

 3-nerved. the first 2-2% lines long; the second a little longer: flowering 

 glumes elliptical, 2-3 lines long, subacute or obtuse usually purplish with 

 a wide scarous tip, scabrous, pubescent on the nerves below: palets linear, 

 as long as the glumes. On cliffs along streams, Oregon and Washington. 



P. saxatilis Scribn. & Williams U. S. Dept. Agr. Div. Agrost. Cir. 9. 

 A closely cespitose perennial : Stems erect, very smooth, 10-18 inches high : 

 sheaths smooth, or the lower ones sparsely pubescent, shorter than the 

 internodes: ligules 1-2 lines long: leaves flat, soft, smooth, 1-2 inches 

 long: panicle lax, 2-4 inches long, its filiform branches ascending, the lower 

 ones about 2 inches long: spikelets compressed, lanceolate, 4-5 lines long, 

 3-5-flowered: empty glumes somewhat unequal obtuse or subacute, 3-nerv- 

 ed, smooth, about 2 lines long: flowering glumes obscurely 5-nerved, 

 minutely scabrous on the back with broad scarious erose-dentate margins, 

 2-3 lines long: palet nearly equalling the glumes, ciliate on the keels, bidentate 

 at the apex. Dry rocky places on Mount Rainier, Washington. 



P. invaginata Scribn. & Williams 1. c. 6. A smooth cespitose per- 

 ennial with numerous intra vaginal shoots and marcescent sheaths : sheaths 

 smooth: ligules acute, 2-2^ lines long: leaves mostly flat, rather narrow, 

 smooth or the margins minutely hispidulous near the base: panicle sub- 

 pyramidal to oblong, its filiform scabrous branches mostly in threes or 

 fives: spikelets compressed, lanceolate, rather loosely 2-5-flowered, 2%-4 

 lines long: empty glumes 3-nerved, narrowly 1 oblong to oblong-ovate, ob- 

 tuse to subacute, the lower 1^-2 lines long, the upper a little longer: flow- 

 ering glumes keeled, oblong-ovate, 5-nerved, minutely scabrous above, 

 pubescent below on the nerves, 2-3 lines long: palets shorter than the 

 glumes, ciliate on the keels. On bluffs along the Columbia river near 

 Hood River Oregon to California. 



§ 3 Atropis Rupr. Fl. Samoj. 64: as Genus. Empty glumes 

 much shorter than the florets: flowering glumes chartaceous, 

 rarely herbaceous, convex on the back; the midnerve often reach- 

 ing the denticulate apex, or extending as a mucro ; the lateral 

 nerves all vanishing at some distance below the broad scarious 

 apex. 



P. Suksdorfli Vasey Beal Grasses N. Am. ii, 574, under Atropis. A 

 densely tufted light green perennial: stems 5-7 inches high : ligules truncate, 

 about 1 line long: leaves of sterile shoots rigid, recurved, conduplicate, pungent 

 pointed, 2-4 inches long, those of the stem erect and shorter: panicle narrow, 

 simple, spike-like, 1-4 inches long: spikelets linear-lanceolate, 1-3-flowered, 

 2-3 lines long: empty glumes linear- lanceolate; the first 3-nerved 2-2)4 lines 

 long; the second a little longer: flowering glumes chartaceous, ovate, 2-2^ lines 

 ong: palets ciliate on the keels. On gravellj" banks near glaciers, Washington. 



P. Vaseyochloa Scribn. U. S Pept. Agr. Div. Agrost. Cir. 9, 1. P. 

 pulchella Vasey. Stems densely tufted, 5-10 inches high: erector ascend- 

 ing from the base, smooth: leaves of the sterile shoots numerous, conduplicate, 

 abruptly pointed, 1-2 inches long, less than 1 line wide: those of the stem 1 or 

 2, b-12 lines long: panicle ovoid or pyramidal, 1-2 inches long, its branches 



