HITCHCOCK AND CHASE—NORTH AMERICAN PANICUM. 149 
Spikelets obovate, obtuse, nearly 3 mm. 
long. * 
Blades about 2 em. wide..........-- 189. P. clandestinum. 
Blades not over 6 mm. wide......-.. 168. P. wilcoxianum. 
Pubescence ascending-pilose. 
Spikelets 2 to 2.5 mm. long. 
Winter blades elongated, 5 to 10 cm. 
long; plants bluish green; spike- 
Iketisy 2A Toatroat Rey ake alse ire anys were ese 145. P. wilmingtonense. 
Winter blades 1 to 3 cm. long; plants 
olivaceous. 
Spikelets about 2.4 mm. long; pan- 
icle open, branches - stiffly 
(3) OZSPEVG NO aN e yay ym re de Alo aia ..-- 148. P.commonsianum. 
Spikelets 2 to 2.1 mm. long; panicle 
rather dense, branches ascend- 
TOE CSS EAN oerea eal ee te 144. P. addisonir. 
Spikelets not over 1.7 mm. long. 
Blades white-margined; spikelets 1.6 
tome] mmmlonevellaptics sass. 152. P. tenue. 
Blades not white-margined; spikelets 
1.3 to 1.4 mm. long, nearly 
plObUIAT ee semen aes aoe toe 147a.P. columbianum 
thinium. 
Sheaths glabrous or puberulent only. e 
Spikelets spherical, not over 1.8 mm. long; 
blades cordate, ciliate at base....-.--. See SPHAEROCARPA 
(p. 250). 
Spikelets not spherical. 
Culms soon prostrate, vine-like; branches 
divaricate. 
Plants bright green; culms lax; spike- 
lets not over 2.1 mm. long. ..-.-.- 114. P. lucidum. 
Plants grayish green; culms stiff; 
spikelets 2.6 mm. long.......--- 115. P. sphagnicola. 
Culms not vine-like; branches not divari- 
cate. 
Spikelets unsymmetrically pyriform, 
strongly nerved; culms wiry..--.- See LANcEARIA (p. 271). 
Spikelets not pyriform. 
Blades elongated, especially the 
upper, about 20 times as long as 
wide; spikelets about 2.5 mm. 
long, on long pedicels.........-- 99. P. bicknellit. 
Blades not elongated. (See con- 
tinuation.) 
(Continuation.) 
Spikelets 2 mm. or more long. 
Spikelets 2.5 to 3 mm. long; blades cordate, usually 1 
cm. or more wide. 
Plants glaucous; basal blades conspicuously ciliate.. 185. P. mutabile. 
Plants not glaucous; basal blades ciliate at base only. 
Blades nearly linear, that is, with parallel mar- 
gins; first glume about half as long as the 
PpUClet Ww MIGXTCAI feces oi cie'c cin elna die oeeels 188. P.albomaculatum. 
