312 
OHIO BIOLOGICAL SURVEY 
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Outer empty glume as long as the spikelet, short acute. P. scribnerianum. 
Outer empty glume 3^ as long as the spikelet, long acuminate. 
„ . , . P. xanthophysum. 
Stem simple or with basal branches only. 16 
Stem at length fasciately branched. 22 
Hairs on the leaf sheath almost pg in. long or longer, spreading, usually 
dense. ^ p Unearifolinm. 
.9. hairs on the leaf sheath, or with hairs less than tV in. long, sometimes 
cihate on the margin. 17 
Leaf blade in. or less wide, usually 18 or more times as long as wide; 
spikelets usually glabrous. 18 
Leaf-blade usually much more than in. wide, never more than 8 times 
longer than wide; spikelets more or less pubescent. 20. 
Leaves much elongated; often 6 to 10 in. long, attenuate at the base. 
P. werneri. 
Leaves not elongated; generally less than 33^ in, long, not attenuate at the 
base, spikelet less than Yg in. long. P. bicknellii. 
Spikelets roundish, not over tV in. long. 20 
Spikelets oblong-elliptic or elliptic, usually in. or more long. 21 
Nodes pubescent with appressed hairs, base of the leaves ciliate, panicle nearly 
as wide as long. P. sphaerocarpon. 
Nodes glabrous, base of the leaves not ciliate; panicle not more than Yi 
wide as long. 
Stems pubescent. 
Stems glabrous. 
Spikelets glabrous. 23 
Spikelets pubescent. 24 
Nodes densely bearded. 
Nodes not bearded. 
Ligule at the top of the leaf sheath minute or absent. 25 
Ligule present. 26 
Nodes of the main stem glabrous or with a few hairs. 
P. polyanthes. 
P. tsugetorum. 
P. boreale. 
P. microcarpon, 
P. dichotomum. 
P. 
P. boreale. 
P. ashei. 
lindheimeri. 
Nodes of the main stem pubescent. 
Upper sheaths glabrous, ciliate on the margin. 
All of the sheaths pubescent. 27 
Upper surface of the leaves glabrous, except for a few long hairs near the 
base. P. tsugetorum. 
Upper surface of the leaves pilose. 28 
Outer empty glume acute; spikelet tV in. long, pubescence on the sheath more 
than tV in. long. P. villosissimum. 
Outer empty glume blunt; spikelet less than in. long; pubescence on the 
sheaths not so dense and less than iV in .long. 29 
Upper surface of the leaf-blade long-pilose; plants yellowish-green. 
P. huachucae 
Upper surface of the leaf-blade long appressed pubescent. 
Spikelet 34 in. or more long. 32 
Spikelet less than 34 In. long. 31 
Spikelet less than in. long. 
Spikelet more than tV in. long. 
Leaf sheaths mostly papillose-hispid; nodes glabrous or short pubescent. 
P. elandestinum. 
Leaf-sheaths glabrous or soft-pubescent. 33 
Nodes glabrous. P. latifolium. 
At least the lower nodes pubescent or bearded. 34 
Panicle narrow, its branches appressed, rarely a little spreading; upper nodes 
at least not bearded. P. xanthophysum. 
Panicle open, its branches spreading; the nodes appressed-pubescent. P. boscii. 
P. implicatum. 
P. polyanthes. 
P. commutatiim. 
