POACEAE 



87 



Stems simple, or sometimes sparingly branched at the nodes : 

 plants usually bright green : hairs on the leaf-sheaths re- 

 flexed. 



Spikelets 1.7-2 mm. long : leaf-blades usually pubescent, some- 

 times nearly glabrous, commonly ciliate on the margins. 

 Spikelets about 2.5 mm. long : leaf-blades glabrous, excepting 



sometimes a few hairs on the margin. 



Stems at length repeatedly dichotomous-branched, forming dense 

 mats : plants grayish green : hairs on the leaf-sheaths, if any, 

 ascending or appressed. 

 Whole plant, excepting the spikelets, glabrous or nearly so, or 



the sheaths and blades sometimes pubescent. 

 Spikelets broadly obovoid, about 2 mm. long. 

 Spikelets obovoid, 2.5-3.5 mm. long. 

 Whole plant, including the upper part of the stem, densely 



villous. 



b. Leaf-blades widely spreading. 

 B. Leaf-blades of the main stem differing from the above, usually lanceolate 



to ovate-lanceolate, sometimes short and linear. 

 Stems simple, or rarely a little branched at the lower nodes, forming 



dense tufts. 

 Leaf-sheaths hirsute. 



Spikelets less than 1.5 mm. long. 

 Spikelets exceeding 1.5 mm. long. 

 Leaf-sheaths glabrous, excepting the ciliate margin ; blades strongly 



and beautifully ciliate on the margins, otherwise glabrous. 

 Spikelets about 1.5 mm. long, glabrous. 

 Spikelets 1.8-2 mm. long, pubescent. 

 Stems finally branching at the upper nodes (sometimes remaining simple 



in number 89), often repeatedly branching. 



* Middle leaf-blades of the main stem less than 1.5 cm. in width, usually 

 less than 1 cm. wide, the base rounded or truncate, sometimes in 

 the broadest ones cordate, 

 f Leaf -sheaths ^glabrous or puberulent, the lower ones sometimes 



with a few scattered long hairs, the margins often ciliate. 

 Stem nearly naked above the base, a single leaf above the mid- 

 dle of the stem. 

 Stems leafy. 

 Nodes barbed. 



Spikelets glabrous : 



A little less than 2 mm. long. 

 About 2.5 mm. long. 

 Spikelets pubescent. 

 Nodes naked. 



Spikelets glabrous. 



Spikelets less than 1.5 mm. long. 



Stems densely tufted, less than 3 dm. tall, finally 

 much-branched and prostrate and forming large 

 mats : spikelets about 1 mm. long. 

 Stems exceeding 6 dm. tall : spikelets about 1.3 mm. 



long. 

 Spikelets 1.5-2 mm. long. 



Leaf-blades ciliate with long hairs, at least for the 



lower half. 

 Leaf-blades not ciliate. 



Primary leaf-blades of the stem large, 9-12 cm. 



long. 



Primary leaf-blades of the stem small, rarely ex- 

 ceeding 6 cm. long. 

 Leaf-blades widely spreading, thin. 



Stems remaining erect, branching at the mid- 

 dle, the late state assuming the form of 

 a little tree. 



Stems becoming prostrate, branching their 

 i: . whole length. 



Leaf -blades erect : 



Thin : stems finally much-branched and pros- 

 trate. 



Ligule membranous, 0.25 mm. long to al- 

 most wanting : spikelets elliptic. 

 Ligule of erect hairs about 1 mm. long : 



spikelets obovoid. 

 Firm, the basal ones thick and much broader 



than the upper. 

 Spikelets 2.5-3 mm. long : 



Elliptic : stems finally much-branched and prostrate. 

 Broadly obovoid : stems erect. 

 Spikelets pubescent. 



Spikelets less than 2 mm. long. 



Leaf- blades ciliate for at least % their length. 



Panicle ovoid : spikelets few, 1.75 mm. long : leaf- 

 blades small. 

 Panicle oblong : spikelets numerous, 1.3 mm. long : 



leaf-blades large. 



Leaf-blades naked on the margins, or sometimes with 

 a few long hairs at the very base. 



46. P. laxiflorum. 

 45. P. pyriforme. 



47. P. neuranthum. 



48. P. angustifolium. 



49. P. consanguineum. 

 107. P. equilaterale. 



42. P. strigomm. 

 46. P. laxiflorum. 



43. P. polycaulon. 



44. P. ciUatum. 



66. P. nudicaule. 



57. P. barbulatum. 



58. P. nemopanthum. 



59. P. Mattamuskcetense. 



68. P. Baldwinii. 

 78. P. octonodum. 



52. P. Nashianum. 

 56. P. Yadkinense. 



55. P. dichotomum. 

 62. P. lutidum. 



62. P. lucidum. 



63. P. curtivaginum. 

 51. P. Roanokense. 



65. P. sphagnicola. 

 116. P. pernervosum. 



52. P. Nashianum. 

 91. P. erectifolium. 



