144 
KEY TO SPECIES, 
Spikelets glabrous. 
Spikelets 3 mm. or more long, strongly nerved. 
Spikelets pointed, blades elongated................... -. 82. 
Spikelets blunt, blades not elongated. 
Spikelets 3.2 to 3.3 mm. long; blades firm; sheaths, or 
some of them, hispid ................--2-.-..-.-.--- 171. P. scribnerianum. 
Spikelets not over 3 mm. long; blades rather thin; 
sheaths glabrous or sparsely hispid...............-170. P. helleri. 
Spikelets less than 3 mm. long. 
Second glume and sterile lemma exceeding the fruit and 
pointed beyond it; spikelets 2.2 to 2.9 mm. long. 
Blades clustered toward the base................----- 101. P. nudicaule. 
Blades not clustered toward the base. 
Sheaths, at least the secondary, hispid. ...........- I8l. P. scabriusculum. 
Sheaths glabrous. 
Blades firm; fruit 1.5 mm. long..........-..-.----- 182. P. cryptanthum. 
Blades thin; fruit nearly 2 mm. long.........-.... 111. P. yadkinense. 
Second glume and sterile lemma not pointed beyond the 
fruit. 
Ligule manifest, | to 3 mm. long. 
Culms rather stout; ligule 2 to 3 mm. long; sheaths 
glabrous.............-..-0.-0000200 0200 ee eee eeeee 116. P. spretum. 
Culms slender; ligule 1 mm. long; sheaths sparsely 
pilose. ..........2.22 222200222 eee eee ee ee eee 159. P. curtifolum. 
Ligule obsolete. 
Spikelets 1.5 mm. or less long. 
Nodes bearded.............-...222220222 00 eee eee 102. P. microcarpon., 
Nodes not bearded. 
Culms and blades pilose..............-.-.----- 90. P. strigosum. 
Culms glabrous. 
Blades conspicuously ciliate; plants branching 
at base only.............-------...-.----. 89. P. polycaulon. 
Blades not ciliate; plants branching from mid- 
dle or upper nodes. 
Vernal culm 50 cm. or more high; spikelets 
turgid, strongly nerved; autumnal form 
erect, with fascicled branches shorter 
than the primary internodes........... 113. P. caerulescens. 
Vernal culms usually much less than 50cm. 
high; autumnal form spreading or re- 
clining. 
Spikelets 1.1 to J.2 mm. long; blades 
rarely as much as 5 cm. long.......-.. 160. P. chamaelonche. 
Spikelets 1.2 to 1.4 mm. long. 
Blades elongated, at least some of them 8 
to 10 cm. long...............------ 161. P. glabrifolium. 
Blades not over 38cm. long......-.---.-- 157. P. ensifolium. 
Spikelets 2 mm. or more long. 
Blades elongated, some of them 20 times as long as 
wide; spikelets 2.2 to 2.8 mm. long. 
Blades erect; branches, when present, from the 
lower nodes only ..............-.-2-------- 85. P. wernert. 
Blades spreading; branches from upper nodes... 99. P. bicknellii. 
2 
La] 
‘CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
. depauperatum, 
