102 



GRAMINEAE (GRASS FAMILY) 



W. Ligule less than 1 mm. long cc. 

 X. Blades velvety on both surfaces ; nodes bearded . 

 85. Blades not velvety ; nodes not bearded y. 

 y. Culms crisp-puberulent ........ 



y. Culms glabrous z. 



. Spikelets 1.5-1.8 mm. long. 



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

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

 Panicle not more than half as wide as long ; blades 



strongly nerved 



Panicle nearly as wide as long ; blades not 



strongly nerved 



. Spikelets 2.2-2.8 mm. long. 



Blades cordate, 1.2-2 cm. wide 



Blades not cordate, 0.6-1.2 cm. wide. 



Blades erect ; fruit covered 



Blades spreading ; fruit exposed at summit 

 '. Sheaths pubescent a. 

 a. Sheaths puberulent, not pilose. 



Spikelets elliptical, 2.6 mm. long 



Spikelets obovoid-turgid, 2 mm. long. 

 Plants erect or spreading ; blades glabrous above . 

 Plants prostrate or creeping ; blades puberulent on both 



surfaces 



a. Sheaths spreading- or appressed-pilose or velvety 6. 

 6. Plants grayish-velvety throughout. 



Spikelets 2.6 mm. long ........ 



Spikelets 1.8 mm. long 



Spikelets 1.3-1 .4 mm. long, very turgid . 

 &. Plants not velvety c. 

 G. Spikelets 2.7-3 mm. long. 



Blades papillose-hirsute on both surfaces 

 Blades glabrous or sparsely silky above .... 

 c. Spikelets less than 2.5 mm. long d. 



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

 cle 1.2-2.5 dm. long 



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



34. P. annulum. 



58. P. Ashei. 



54. P. ensifolium. 



56. P. polyanthes. 



55. P. sphaerocarpon. 



57. P. commutatum. 



82. P. boreale. 



33. P. mattamuxkeeiense 



58. P. Ashei. 



60. P. lancearium. 



61. P. patulum. 



68. P. sooparium. 



44. P. lanuginoHut 



45. P. auburn e. 



67. P. Wilcoxianum. 

 49. P. 



). P. scabriusculum. 



shorter e. 

 6. Pubescence spreading /. 

 /. Spikelets 2.2-2.4 mm. long. 



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

 Plants papillose-hispid on sheaths and sparsely 



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

 f. Spikelets 1.3-1.9 mm. long g. 



y. Blades stiff, glabrous above or with a few hairs . 43. P. tennesseense. 

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

 h. Upper surface of blades with erect hairs 3-5 mm. long. 

 Culms branching very early ; spikelets 1.8- 



1.9 mm. long 46. P. praecocius. 



Culms branching after maturity of primary 



panicle ; spikelets not over 1.5 mm. long. 



Axis of panicle long-pilose . . . . 39. P. implicatum. 

 Axis of panicle nearly glabrous . . .40. P. meridional^. 

 A. Upper surface of blades with short or some- 

 what appressed pubescence. 



Blades stiif; spikelets obovate . . . .38. P.huachucae. 

 Blades lax; spikelets elliptical (88) P. huachucae, v. silvicola. 



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. tsugetorum. 



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



plants gray-green 53. P. columbianum. 



i. Culms with short or long appressed pubescence j. 

 j. Ligule obsolete or nearly so. 



Spikelets 2.5 mm. long 50. P. Commonsianum. 



Spikelets 2-2.2 mm. long 51. P. Addisonii, 



j. Ligule 2-3 mm. long. 



Pubescence on lower sheaths spreading . . 40. P. meridionals. 

 Pubescence on lower sheaths appressed. 

 Blades glabrous on upper surface; spikelets 



1.2 mm. long 87. P. leueothrias. 



Blades pubescent on upper surface ; spikelets 



1.5-1.9 mm. long. 

 Spikelets 1.5 mm. long ; panicles not over 



8 cm. long 41. P. oricola. 



Spikelets 1.9 mm. long ; panicles 3-5 cm. 



long 42. P. subvillosum. 



