HITCHCOCK AND CHASE NORTH AMERICAN PANICUM. 145 



Blades not elongated, about 10 times as long as wide. 

 Culms soon prostrate, vine-like; branches divari- 

 cate. 

 Plants bright green; culms lax; spikelets not 



over 2.1 mm. long 114. P. luddum. 



Plants grayish green; culms stiff; spikelets 2.5 



mm. long 115. P. sphagnicola. 



Culms not vine-like; branches not divaricate. 

 Spikelets 2.3 to 2.6 mm. long. 

 Blades, or some of them, at least 8 mm. wide; 



fruit papillose-roughened 166. P. webberianura. 



Blades not over 6 mm. wide; fruit smooth 



and shining 167. P. patentifolium. 



Spikelets 2 mm. long. 

 Culms wiry, crisp-puberulent ; blades ciliate 



at base 164. P. lancearium. 



Culms glabrous; blades not ciliate. 

 Blades erect, firm; spikelets turgid, 



strongly nerved ; plants grayish olive . 112. P. roanokense. 

 Blades spreading; spikelets not turgid. 

 Nodes glabrous; autumnal form erect, 



branched like a little tree 109. P.dichotomum. 



Nodes, at least the lowest, usually 

 bearded; autumnal form topheavy- 



reclining 110. P. barbulatum. 



Spikelets pubescent. ^^^^^^ ^ V-^.Vrx^sL^S_^ r^A^:^ 



Spikelets 3 mm. or more long. . >''^j**f i% ' crSgr>C5u-<v. '^i -r-rxj-orv , ^ 



Blades elongated, those of the mid-culm at least 15 times as 

 long as wide. 

 Secondary panicles from basal sheaths only. 



Spikeletp pointed, about 3.5 mm. long 82. P. depauperatiim.. 



Spikelets blunt, 3 mm. or less long 83. P. perlongum. 



Secondary panicles from upper branches. 

 Spikelets attenuate at base, pustulose-pubescent; 



lowermost sheaths softly villous 95. P. fusiforme. 



Spikelets not attenuate at base, not pustulose; lower- 

 most sheaths glabrous or hispid. 



Upper leaves approximate; sheaths glabrous 187. P. equilaterale. 



Upper leaves distant; at least lower sheaths hispid . 180. P. aculeatum. 

 Blades not elongated, usually less than 10 times as long as 

 wide. 

 Blades velvety-pubescent beneath. 

 Spikelets 3 mm. long; plants velvety -villous through- 

 out 169. P. mahophyllum. ql 



Spikelets 4 mm. or more long. ^ "" 



Sheaths ascending-hirsute; ligule 3 to 4 mm. long. . 173. P. ravenelii. 



Sheaths downy-pubescent; ligule obsolete 191a. P. bosdi molle. 



Blades not velvety-pubescent beneath. 

 Sheaths glabrous or minutely puberulent only. 



Nodes bearded; spikelets 4 mm. or more long 191. P. bosdi. 



Nodes not bearded; spikelets not over 3.8 mm. long. 

 Spikelets 3.5 to 3.8 mm. long; blades 2 cm. or 



more wide 190. P. latifolium. 



41616°— VOL 15—10 10 



