HITCHCOCK AND CHASE—NORTH AMERICAN PANICUM. 
Culms single or few in a tuft; spikelets turgid, 2.7 to 3 
mm. long..........2...20..2 202222 e eee eee eee 83. 
Culms in large tufts; spikelets not turgid, not over 2.7 
mm. long, 
Sheaths pilose. ........2...2.2-.22-.-20-0-02-220c0eee 84. 
Sheaths glabrous.............2.-2....0..000-22000-- 85. 
Blades usually not elongated; secondary panicles not at 
the base. 
Spikelets attenuate at base, mostly prominently pustu- 
lose; blades narrow, stiff, strongly nerved, tapering 
from base to apex. 
Nodes bearded; plants grayish-villous; autumnal 
blades flat. 
Spikelets 2 mm. long...............2-.-..--.---. 92. 
Spikelets 2.5 to 2.8 mm. long...................-- 93 
Nodes not bearded; plants villous only at the base, or 
nearly glabrous. 
Autumnal blades flat; lower panicle branches 
spreading or deflexed wee cece eee eee eee eeee 
Autumnal blades involute; lower panicle branches 
more or less ascending. 
Plants glabrous or nearly, so; autumnal culms 
erect. 
Spikelets subsecund along the suberect panicle 
branches. ..........22-2--2--220.2200000- 98. 
Spikelets not subsecund; panicle loose and 
OpeN......-2 22. eee eee ee eee eee eee eee 97 
Plants pubescent, at least on the lower half. 
Spikelets about 2.4 mm. long; vernal blades 7 
to 12cm. long, autumnal blades not falcate. 96. 
Spikelets not over 2 mm. long; vernal blades 
4 to 6 cm. long, autumnal blades falcate. . 
Spikelets not attenuate at base. 
Sheaths retrorsely pilose; blades soft and lax. 
Panicle branches ascending, forming a compact 
panicle; spikelets 1.6 mm. long............... 
Panicle branches loosely spreading. 
Blades ciliate and more or less pilose on the sur- 
face; spikelets 2 mm. long.................. 
Blades glabrous or nearly so on the surface and 
margin; 
Sheaths not retrorsely pilose. 
Ligule manifest, mostly 2 to 5 mm. long. 
Sheaths, or all but the lowest glabrous; spike- 
lets not over 1.6 mm. long. 
Panicle narrow, one-fourth to one-third as wide 
Panicle open, nearly as wide as long. 
Spikelets 1.5 mm. long.................---- 117. 
Spikelets 1.1 mm. long.................-... 
Sheaths pubescent. 
91. 
87a. 
spikelets 2.2 mm. long. .......-... 86. 
P 
. P, 
~ 
P, 
_ P 
. 
. #2, 
P. 
. longiligulatum. 
P. 
P. 
147 
. perlongum. 
. Linearifolium. 
. wernert. 
. chrysopsidifo- 
lium. 
consanguineum. 
. angustifolium, 
neuranthum, 
.ovinum. 
. arenicoloides. 
. aciculare. 
ralapense stric- 
tirameum. 
. calapense. 
laxiflorum. 
spretum. 
lindheimeri. 
