MANUAL OF THE GRASSES OF THE UNITED STATES 103 



Ligule prominent, easily seen in side view, 5 to 7 mm. long 43. P. longiligula. 



Blades flat or, if involute, rather lax or soft. 



Panicle branches slender, spreading or drooping, the lower naked and simple for 3 to 4 cm. 



or more 44. P. autumnalis. 



Panicle branches not long and spreading. 



Panicle broadly pyramidal, condensed, about as broad as long, the lower branches 



spreading. Spikelets broad, subcordate 45. P. alpina. 



Panicle longer than broad. 



Panicle nodding, the lower branches slender, arcuate-drooping. 



46. P. STENANTHA. 



Panicle erect, the lower branches short (see also P. gracillima). 



Panicle rather loose, lower branches naked below, ascending (see also P. macro- 

 lada). 

 Plants glaucous, culms flattened ; panicle rather narrow. 



Spikelets 2- or 3-flowered; panicle 3 to 7 cm. long 47. P. glauca. 



Spikelets 3- to 6-flowered; panicle 6 to 16 cm. long 48. P. glaucantha. 



Plants not glaucous; culms terete, rather lax 49. P. fernaldiana. 



Panicle narrow, condensed, the branches short (see also P. unilateralis) . 

 Culms rather lax; ligule minute; glumes about 4 mm. long. 



50. P. PATTERSONI. 



Culms stiff, ligule about 1.5 mm. long, glumes about 3 mm. long. 



51. P. RUPICOLA. 

 6. Epiles 



Panicle open, 10 to 15 cm. long. Blades involute, slender 52. P. involuta. 



Panicle contracted or, if open, less than 10 cm. long. 

 Blades scabrous, filiform, mostly basal. 



Spikelets 7 to 9 mm. long; lemmas 4.5 to 6 mm. long, mostly smooth. 



53. P. cusickii. 



Spikelets 6 to 7 mm. long; lemmas about 4 mm. long, scabrous 54. P. napensis. 



Blades glabrous. 



Lemmas minutely pubescent at base 55. P. unilateralis. 



Lemmas glabrous. 



Blades of the culm 2 to 3 mm. wide, flat, those of the innovations slender and filiform. 



56. P. EPILIS. 

 Blades of the culm and innovations similar. Panicle few-flowered. 



Panicle short, open, the capillary branches bearing 1 or 2 spikelets. Culms 10 to 



20 cm. tall 57. P. vaseyochloa. 



Panicle narrow. 



Lemmas 5 to 6 mm. long; panicle usually pale or silvery 58. P. pringlei. 



Lemmas less than 4 mm. long; panicle usually purple. 



Glumes about as long as the first and second florets; panicle mostly not exceed- 

 ing the short soft blades. 

 Glumes and lemmas smooth, the lemmas erose at summit. 



59. P. LETTERMANI. 



Glumes and lemmas scabrous, the lemmas acute, scarcely erose. 



60. P. MONTEVANSI. 



Glumes shorter than the first floret; panicle usually much longer than the 

 usually stitf blades 61. P. leibergii. 



7. Scabrellae 



Sheaths somewhat scabrous 62. P. scabrella. 



Sheaths glabrous. 



Panicle rather open, the lower branches naked at base, ascending or somewhat spreading; 



culms usually decumbent at base. 63. P. gracillima. 



Panicle contracted, the branches appressed or at anthesis somewhat spreading. 



Culms slender, on the average less than 30 cm. tall; numerous short innovations at 



base. Blades usually folded 64. P. secunda. 



Culms stouter, on the average more than 50 cm. tall; innovations usually not numerous. 



65. P. CANBYI. 



8. Nevadenses 



Sheaths scaberulous. Ligule long, decurrent 66. P. nevadensis. 



Sheaths glabrous. 



Ligule prominent; blades broad and short 67. P. curtifolia. 



Ligule short; blades elongate. 



Blades involute 68. P. juncifolia. 



Blades flat _ 69. P. ampla. 



