292 Bulletin No. 205 [March, 



cc. Spikelets less than 3 mm. long. 



d. Blades very long- ami nnrrow, not over 5 mm. wide, nsual'.y all 

 erect from the base of the plant and nsnally longer than the 

 panicle nntil it is matnre; spikelets 2.2 to 2.7 mm. long; 

 sheaths pilose. P. Uncarifolium 



dd. Blades not elongated, not in a tuft at the base of the plant, the 

 panicle always considerably above the leaves; sheaths smooth, 

 or the lowermost sometimes puberulent. 

 e. Spikelets more than 2 mm. long, pointed; sheaths with pale 

 glandular spots. P. yadkinensc 



ce. Spikelets 2 mm. or less long, not pointed. 

 f. Nodes bearded. 



g, Ligule not present; spikelets 1.5 to 1.6 mm. long. 



P. microearpon 

 gg. Ligule present; spikelets 2 mm. long; at least the 

 lower nodes bearded; fruit always covered by the 

 second glume and sterile lemma. P. harbiilatum 

 ff. Nodes not bearded; spikelets 2 mm. long; the fniit ex- 

 posed at tip, never quite covered by the second glume 

 and sterile lemma. , P. dichotomum 



aa. Spikelets more or less pubescent. 



b. Blades broad, usually more than 1.5 cm. wide, cordate at base; culms 

 stout, usually two feet or more high; spikelets over 2.5 mm. long. 

 c. Sheaths, at least the lower ones, hispid, the hairs arising from prom- 

 inent papillae; spikelets 2.7 to 3 mm. long. P. clandesiinu in 

 cc. Sheaths smooth, or with a few soft hairs. 



d. Nodes smooth; spikelets less than 4 mm. long. P. latifolium 



dd. Nodes bearded; spikelets 4 to 4.5 mm. long. P. boscii 



bb. Blades narrow, at least not over 1.5 cm. wide, usually not cordate at base; 

 culms never as stout, rarely as tall, as in the preceding species. 

 c. Spikelets 2 mm. or more long. 



(I. Blades much elongated, the length usually more than fifteen times 

 the breadth, less than 5 mm. wide, the leaves growing mostly 

 erect from the base and forming tufts. 

 e. Spikelets about 3.5 mm. long, pointed or beaked. 

 ' P. depmtperatum 



ee. Spikelets 3 mm. long or less, not pointed or beaked. 



f. Culms in small tufts; spikelets 2.7 to 3.2 mm. long, almost 

 as broad as long. P. pcrlongum 



ff. Culms in large tufts; spikelets 2.2 to 2.7 mm. long, dis- 

 tinctly longer than broad. P. lineari folium 

 dd. Blades usually not elongated, generally over 5 mm. wide; leaves 

 not all clustered at the base of the plant, but distributed along 

 the culm, 

 e. Spikelets more than 3 mm. long; culms stout, erect, with stiff 

 blades, and usually pubescent sheaths, 

 f. Plants densely pubescent thruout, the hairs arising from 

 small papillae, those on the sheaths spreading; panicle 

 narrow, always longer than wide. P. leihergii 

 ff. Plants not densely pubescent thruout, usually with few 

 hairs on the blades, the upper surface normally smooth ; 

 panicle about as wide as long, 

 g. Spikelets distinctly longer than broad, somewhat 

 pointed, usually pubescent; plants olivaceous, pu- 

 bescence appressed. P. oligosanthes 

 gg. Spikelets nearly as broad as long, blunt, usually 

 nearly smooth ; plants always bright green or yel- 

 lowish green, pubescence not appressed. 



P. scrihnerkinum 

 ec. Spikelets less than 3 mm. long. 



f. Leaves densely i:»ubescent on both surfaces, the entire 

 plant pubescent; spikelets 2.2 to 2.4 mm. long. 



