HITCHCOCK AND CHASE—NORTH AMERICAN PANICUM. 149 
Spikelets obovate, obtuse, nearly 3 mm. 
long. 
Blades about 2 cm. wide. ........... 189. P. clandestinum. 
Blades not over 6 mm, wide......... 168. P. wilcorianum. 
Pubescence ascending-pilose. 
Spikelets 2 to 2.5 mm. long. 
Winter blades elongated, 5 to 10 cm. 
long; plants bluish green; spike- 
lets 2mm. long................. 
Winter blades 1 to 3 cm. long; plants 
olivaceous. 
Spikelets about 2.4 mm. long; pan- 
icle open, branches - stiffly 
spreading.............2.....-. 
Spikelets 2 to 2.1 mm. long; panicle 
rather dense, branches ascend- 
ING... 22. eee eee eee eee eee 
Spikelets not over 1.7 mmm. long. 
Blades white-margined; spikelets 1.6 
145. P. wilmingtonense, 
143. P.commonsianum. 
144 
. P. addisonii. 
° to 1.7 mm. long, elliptic......... 152. P. tenue 
Blades not white-margined; spikelets 
1.3 to 14 mm. long, nearly 
globular......2....2.0.0..00202.-. 147a.P. columbianum 
thinium. 
Sheaths glabrous or puberulent only. 
Spikelets spherieal, 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 2.5 mm. long.......... 
Culms not vine-like; branches not divari- 
cate. 
Spikelets unsymmetrically pyriform, 
strongly nerved; culms wiry..... 
Spikelets not pyriform. 
Blades elongated, especially the 
upper, about 20 times as long as 
wide; spikelets about 2.5 mm. 
long, on long pedicels........... 
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. . 
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 
spikelet; Mexican....... sec eee eee eeeee 
115 
99 
185 
. P. sphagnicola. 
See LANCEARIA (p. 271). 
. P. bicknellit. 
. P. mutabile. 
= 
. P.albomaculatum. 
