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Boa Ss GRAMINEA 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, 14-\% line 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 2-244 
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 2-214 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. 8. 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- 
ennia] with numerous intravaginal! shoots and marcescent sheaths: sheaths 
smooth : ligules acute, 2-214 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, 224-4 
lines long: empty glumes 3-nerved, ,narrowly oblong to oblong-ovate, ob- 
tuse to subacute, the lower 114-2 lines long, the upper a little longer: flow- 
ering glumes keeled, oblong-oyate, 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 Arropis 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 2-24 lines 
- long; the second a little longer: flowering glumes chartaceous, ovate, 2-244 lines 
ong: palets ciliate on the keels. On gravelly banks near glaciers, Washington, 
P. Vaseyochloa Scribn. U. S. Dept. Agr. Div. Agrost. Cir. 9, 1. P. 
pulchella Vasey. Stems densely tufted, 5-10 inches high: erect or 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, 6-12 lines long: panicle ovoid or pyramidal, 1-2 inches long, its branches 
