GRASS FAMILY 75 



XIIT. MULTNOMAE. 



One species. 40. P. Multnomae. 



XIV. E PILES. 



Plant green; lemma purple or dark green, abruptly acute; ligules acute. 



Blades of the stem-leaves about 3 mm. wide, flat; lemma more than 5 mm. long, 



dark purple. 41. P. paddensis. 



Blades of the stem-leaves 1-2 mm. wide; lemma 4-5 mm. long 



Lemma purple, minutely scabrous, nearly smooth. 42. P. Cusickii. 



Lemma green, only tinged with purple, hispidulous-scabrous. 



43. P. epilis. 

 Plant pale; lemma very pale, long-attenuate or subcuspidate; leaves all filiform. 



Ligules lanceolate, acuminate. 



Panicle thick; branches with several 5-7-flowered spikelets; leaves very scabrous. 



44. P. scaberrima. 



Panicle narrow, slender; branches very short, with 1-2, only 2-4-flowered spike- 

 lets. 45. P. nematophylla. 



Ligufes oblong, 1 mm. long, truncate; panicle dense and spike-like. 



46. P. subaristata. 



XV. GRACII.LIMAE. 



Lemma linear-lanceolate. 5-6 mm. long. 47. P. idahoensis. 



Lemma ovate, 4-5 mm. long. 



Plant 1-3 dm. high; panicle with ascending branches and many spikelets. 



48. P. gracillima. 

 Plant 0.5-1.5 dm. high; panicle with divaricate branches and few spikelets. 



49. P. Vaseyochloa. 



XVI. FENDLERIAXAE. 



Ligules 5-7 mm. long, acute or acuminate. 50. P. longiligula. 



Ligules short, rounded or truncate, or those of the innovations obsolete. 

 Leaf-blades erect; spikelets 3-5- (rarely 6-7-) flowered. 



Lemma oblong; leaf-blades very slender, scabrous. 51. P. scabriuscula. 



Lemma ovate; leaf-blades more rigid. 



Panicle very narrow, its branches erect and spikelet-bearing to the base; 

 lemma 4 mm. long. 52. P. longipedunculata. 



Panicle more open, its branches ascending, usually naked at the base. 



Plant low; panicle short; lemma 3.5-4 mm. long. 53. P. brevipaniculata. 

 Plant tall; panicle elongated; lemma 5 mm. long. 54. P. Fendleriana. 

 Leaf-blades spreading; spikelets 7-9- (rarely 5-6-) flowered. 55. P. Eatoni. 



XVII. BUCKLEYANAE. 



Ligules lanceolate, acuminate or attenuate. 



Empty glumes strongly nerved, elongate-lanceolate, almost equalling the very scab- 

 rous or strigose lemma. 



Leaves 4-6 mm. wide, flat. 56. P. Canbyi. 



Leaves 1-3 mm. wide, conduplicate or involute. 



Lemma strongly scabrous; leaves stiff; plant stout. 57. P. nevadensis. 

 Lemma strigose, at least below; leaves filiform, flaccid; plant slender. 



58. P. Helleri. 

 Empty glumes not strongly nerved, ovate-lanceolate, usually much shorter than the 



lemma. 

 Plant yellowish green; spikelets yellowish or straw-colored. 



Lemma merely scabrous. 59. P. laevigata. 



Lemma more or less strigose on the lower portion. 60. P. lucida. 

 Plant dark green; spikelets dark green or purplish. 



Leaf-blades almost 2 mm. wide, flat or conduplicate; lemma more than 4 mm. 



long. 61. P. Buckley ana. 



Leaf-blades le^s than 1 mm. wide, filiform, involute; lemma less than 4 mm. long. 



62. P. Sandbergii. 

 Ligules 1-2 mm. long, truncate, rounded or abruptly acute. 



Plant 2-4 dm. high; leaves mostly basal and stiff, short, seldom 8 cm. long; ligules 



rounded. 63. P. junci folia. 



Plant taller, 4-10 dm. high, leafy; leaves longer. 



Internerves of the lemma glabrous; nerves silky. 36. P. glaucifolia. 



Internerves of the lemma as well as the nerves scabrous. 



Leaves filiform, less than 1 mm. wide. 64. P. brachyglossa. 



Leaves flat or involute, but not filiform, 2-5 mm. wide. 

 Ligules ovate or rounded, acute or obtuse; leaves soft. 



65. P. confusa. 

 Ligules truncate; leaves stiff. 



Inflorescence very narrow; branches erect. 66. P. truncata. 



Inflorescence more open, lobed; branches ascending. 



67. P. ampla. 



1. P. annua L. Stems usually decumbent and branched at the base or 

 erect; ligules rounded at the apex, 2 mm. long; leaf-blades flat, flaccid, 1-10 cm. 

 long, 1.5-3 mm. wide; panicle 1-10 cm. long; spikelets 3-5 mm. long; empty 

 glumes smooth, the first lanceolate, acute, 1.5 mm. long, the second obtuse, 



