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. ivilcoxianum. 



Pubescence ascending-pilose. 

 Spikelets 2 to 2.5 mm. long. 



Winter blades elongated, 5 to 10 cm. 

 long; plants bluish green; spike- 

 lets 2 mm. long 145. P. wilmingtonense. 



Winter blades 1 to 3 cm. long; plants 

 olivaceous. 

 Spikelets about 2.4 mm. long; pan- 

 icle open, branches stiffly 



spreading 143. P .commonsianum. 



Spikelets 2 to 2.1 mm. long; panicle 

 rather dense, branches ascend- 

 ing 144. P. addisonii. 



Spikelets not over 1.7 mm. long. 

 Blades white-margined; spikelets 1.6 



to 1.7 mm. long, elliptic 152. P.tenue. 



Blades not white-margined; spikelets 

 1.3 to 1.4 mm. long, nearly 



globular 147a. P. columbianum 



thinium. 

 Sheaths glabrous or puberulent only. 



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 2.5 mm. long 115. P. sphagnicola. 



Culms not vine-like ; branches not divari- 

 cate. 

 Spikelets unsymmetrically pyriform, 



strongly nerved; culms wiry SeeLANCEARiA(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. bicknellii. 



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 

 spikelet; Mexican 188. P.albomaculatum. 



