148 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Spikelets abruptly pointed; blades cordate; 
Spikelets not pointed at maturity; blades not 
cordate. 
Ligule 1 mm. long; sheaths sparsely pilose; 
spikeletsil/4 mm longe  ee ee asap 159. 
Ligule usually more than 1 mm. long. 
Ligule 1 to 1.5 mm. long; culms and 
sheaths appressed-pubescent; spike- 
lets 1.5 to 1.9 mm. long. 
Spikelets 1.8 to 1.9 mm. long; plants 
blmishiereent: #2 = 7 5s ee eee eee 146. 
Spikelets 1.5mm. long, nearly globular; 
plants olivaceous........--------:- 148. 
Ligule 2 to 5 mm. long. 
Spikelets 1 to 1.3 mm. long; culms and 
sheaths softly appressed-pubescent. 
Spikelets 1.2 to 1.3 mm. long......... 118. 
Spikelets not over 1 mm. long...-.-..120. 
Spikelets mostly more than 1.5 mm. 
Miexa Cais 2 ein SY (Bene Metals ep ied a eee ae 179. P. viscidellum. 
P. curtifolium. 
P. tsugetorum. 
P. oricola. 
P. leucothriz. 
P. wrightianum. 
long, if less, pubescence spreading. See LANUGINOSA 
Ligule obsolete or less than 1 mm. long. 
Nodes bearded (P. scoparium may appear to be 
bearded). 
Spikelets nearly 3 mm. long; plants velvety- 
willous throushoutayseee- see ae eaaeeaee 169. 
Spikelets rarely as much as 2.5 mm. “sae: 
plants not pubescent throughout. 
Spikeletswe arto tee mmiplons essa seers 102. 
Spikelets 2 mm. or more long. 
Blades all velvety; autumnal form spar- 
img lyabranchedey tessa eee aes 105. 
Blades glabrous, or only the lower pubes- 
cent or velvety. 
Spikelets 2 mm. long; autumnal form 
_profusely branching. 
Fruits slightly exposed at maturity; 
upper sheaths viscid-spotted. ---.- 103. 
Fruits covered at maturity; sheaths 
not viscid-spotted; Mexican- --..104. 
Spikelets 2.2 mm. or more long; autum- 
nal form less profusely branching. 
Sheaths and upper nodes glabrous. . . . 107. 
Lower sheaths and all nodes pubes- 
GORGE eb sais wet CN ae eg Beer 106. 
Nodes not bearded. 
Plants densely gray-velvety throughout, a 
viscid, glabrous ring below the nodes. .--.-- 178. 
Plants not gray-velvety. 
Sheaths or some of them pilose or hispid. 
Pubescence papillose-hispid. 
Spikelets ovate, pointed, 2.3 to 2.6 mm. 
(p. 208). 
P. malacophyllum. 
P. microcarpon. 
P. annulum. 
P. nitidum. 
P. multirameum. 
P. clutet. 
; \ 
P.  mattamuskee- 
tense. 
P. scoparium. 
. P. scabriusculum. 
