180 CONTRIBUTIONS FROM THE NATIONAL: HERBARIUM. 
Nodes, at least the lower, bearded. 
Spikelets 1.5 to 1.6 mm. long, glabrous (occasional in- 
dividuals with pubescent spikelets)........-.-.-.-- 102. 
Spikelets 2 mm. or more long. 
Spikelets glabrous, 2 mm. long; autumnal form top- 
heavy-recliumine a2 ee eee eee eee 110. 
Spikelets pubescent. 
Blades all velvety; autumnal form sparingly 
ora Clie ciey pe iat ea aera epee a eee es hel Lats 4 105. 
Blades glabrous, or only the lower pubescent or 
velvety; autumnal form freely branching. 
Spikelets 2 mm. long; autumnal form pro- 
fusely branching. 
Fruits slightly exposed at maturity; 
upper sheaths viscid-spotted; 
autumnal form erect or reclining. - 103. 
Fruits covered at maturity; sheaths not 
viscid - spotted; autumnal form 
decumbent, with  flabellate - 
fascicled branches; Mexican...--- 104. 
Spikelets 2.2 mm. or more long; autumnal 
form less profusely branching. 
Sheaths and upper nodes glabrous. - --- - 107. 
Lower sheaths and all nodes pubescent. - 106. 
Nodes not bearded. 
Spikelets pubescent. 
Culms erect, never becoming vine-like. 
Primary blades spreading; panicles purplish; 
Inuit. exposed ab suMminalt e-as = seers ae 107. 
Primary blades erect; panicles green; fruit cov- 
ered (wood forms with spreading blades 
may be distinguished from P. dichotomum 
by pubescent spikelets, 2.2 mm. long)... .108. 
Culms soon prostrate, vine-like; branches divaricate. 
Plants bright green, culms lax; spikelets not 
Owe Boll mM, NOW ocackasaacecdocasosoase 114. 
Plants grayish green, culms stiff; spikelets 2.5 
BOG ATTY Kol ATS AME UG ela catalase 115 
Spikelets glabrous. 
Culms soon prostrate. 
Plants bright green, culms lax; spikelets not 
Owen Balbinmone Ao oe Coocascesasacadeseue 114. 
Plants grayish green, culms stiff; spikelets 2.5 
Culms erect, or the autumnal form topheavy, never 
prostrate. 
Spikelets not over 1.6 mm. long; panicles nar- 
row; plants glaucous bluish green..-....-.- 118. 
Spikelets 2 mm. or more long; panicles open. 
Blades erect, firm; spikelets turgid, strongly 
nerved; plants grayish olive green....112. 
Blades spreading; spikelets not turgid. | 
P. microcarpon. 
P.. barbulatum. 
P. annulum. 
P. nitidum. 
P. multirameum. 
P. clutet. 
P. mattamuskeet- 
ense. 
P. clutet. 
P.. boreale. 
P. lucidum. 
P. sphagnicola. 
P. lucidum. 
P. sphagnicola. 
P. caerulescens. 
P. roanokense. 
