GRAMINEAE (GRASS FAMILY) 



w. Ligule less than 1 mm. long x. 



x. Blades velvety on both surfaces ; nodes bearded . . . 34. P. annulum. 

 so. Blades not velvety ; nodes not bearded y. 



y. Culms crisp-puberulent 58. P. Ashei. 



y. Culms glabrous *. 



z. Spikelets 1.5-1.8 mm. long. 



Culm-blades not over 2 cm. long ; spikelets elliptical 54. P. enxifolium. 

 Culm-blades 6-20 cm. long: spikelets spheroidal. 

 Panicle not more than half as wide as long; blades 



strongly nerved 56. P. j><>lyant/i?n. 



Panicle nearly as wide as long ; blades not 



strongly nerved 55. P. fiphaerocarpo/t 



. Spikelets 2.2-2.8 mm. long. 



Blades cordate, 1.2-2 cm. wide 57. P. com muta tin,,. 



Blades not cordate, 0.6-1.2 cm. wide. 



Blades erect ; fruit covered 82. P.boril,'. 



Blades spreading ; fruit exposed at summit . . 33. P. 

 . Sheaths pubescent a. 

 a. Sheaths puberulent, not pilose. 



Spikelets elliptical, 2.6 mm. long 58. P. Axhei. 



Spikelets obovoid-turgid, 2 mm. long. 



Plants erect or spreading; blades glabrous above . . 60. P. lancearium. 

 Plants prostrate or creeping ; blades puberulent on both 



surfaces 61. P. patulum. 



a. Sheaths spreading- or appressed-pilose or velvety b. 

 b. Plants grayish-velvety throughout. 



Spikelets 2.6 mm. long 68. P. scoparium. 



Spikelets 1.8 mm. long 44. P. lanuginotum. 



Spikelets 1.3-1.4 mm. long, very turgid . . . .45. P. an >>/'///,. 

 b. Plants not velvety c. 

 c. Spikelets 2.7-3 mm. long. 



Blades papillose-hirsute on both surfaces . . .67. P. Wilcoxianum. 



Blades glabrous or sparsely silky above . . . . 49. P. ovale. 

 c. Spikelets less than 2.5 nun. long d. 

 d. Spikelets ovate, pointed; blades 1.5-2.5 dm. long; pani- 



. cle 1.2-2.5 dm. long 69. P. scabriusculum 



d. Spikelets obovate or elliptical, blunt ; blades and panicle 



shorter e. 



6. Pubescence spreading /. 

 /. Spikelets 2.2-2.4 mm. long. 



Plants very villous ; autumnal state prostrate . 48. P. 

 Plants papillose-hispid on sheaths and sparsely 



hispid on blades; autumnal state erect . . 47. P. 

 f. Spikelets 1.3-1.9 mm. long g. 



g. Blades stiff, glabrous above or with a few hairs . 43. P.tiinu .x.vfc//AV. 

 g. Blades pubescent above, or if glabrous lax h. 

 h. Upper surface of blades with erect hairs 8-5 mm. long. 

 Culms branching very early; spikelets 1.8- 



1.9 mm. long 46. P. prafcociux. 



Culms branching after maturity of primary 



panicle ; spikelets not over 1.5 mm. long. 



Axis of panicle long-pilose . . . .39. /'. i//i/>ti<-nfit>/>. 

 Axis of panicle nearly glabrous . . .40. I', meridional*. 

 h. Upper surface of blades with short or some- 

 what appressed pubescence. 



Blades stiff ; spikelets obovate . . . .88. P. hn acini cae. 

 Blades lax; spikelets elliptical (88) P.huackueae, v. si/cico/a. 



6. Pubescence not spreading i. 



i. Culms crisp-puberulent or crisp-pubescent; ligule 



nearly obsolete. 

 Spikelets 1.9 mm. long; blades 5-6 cm. long; 



plants blue-green 52. P. txugetorum. 



Spikelets 1.7 mm. long; blades 3-5 cm. long; 



plants gray -green 58. P. Columbia num. 



i. Culms with short, or long appressed pubescence^'. 

 j. Ligule obsolete or nearly so. 



Spikelets 2.5 mm. long 50. 



Spikelets 2-2.2 mm. long 51. 



j. Ligule 2-3 mm. long. 



1'iil.escenco on lower eheaths spreading . . 40. /'. meridional*. 

 Pubescence on lower sheaths apprcssed. 

 Blades glabrous on upper surface; spikelets 



1.2 mm. long 87. P. 



Blades pubescent on upper surface ; spikelets 



1.5-1.9 mm. long. 

 Spikelets 1.5 mm. long; panicles not over 



:; cm. long 41. P. 



Spikelets 1.9 mm. long; panicles 3-"> cm. 



long 42. /'. 



