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. lucidum. 
Plants grayish green; culms stiff; spikelets 2. 5 
mm. long........--2..2.2....2.2202220-2- 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. webberianum. 
Blades not over 6 mm. wide; fruit smooth 
and shining.................2220.2002. 167. P. patentifolium. 
Spikelets 2 mm. long. 
Culms wiry, crisp-puberulent; blades ciliate 
at base... 22.22.2222 2 2 eee eee eee 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. 
Spikelets 3 mm. or more long. 
Blades elongated, those of the mid-culm at least 15 timesas 
long as wide. 
Secondary panicles from basal sheaths only. 
Spikelets pointed, about 3.5 mm. long.............. 82. P. depauperatum. 
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- 
08 169. P. malcophyllum. 
Spikelets 4 mm. or more long. 
Sheaths ascending-hirsute; ligule 3 to 4 mm. long. . 173. P. ravenelii. 
Sheaths downy- pubescent; ligule obsolete......... 19la. P. boscti molle. 
Blades not velvety-pubescent beneath. 
Sheaths glabrous or minutely puberulent only. 
Nodes bearded; spikelets 4 mm. or more long...... 191. P. boscii. 
Nodes not bearded; spikelets not over 3.8 mm. long. 
Spikelets 3.5 to 3.8 mm. long; blades 2 cm. or 
more Wide..... 2.22.2... ce... cece eee eee ee 190. P. latifolium. 
41616°—voL 15—10—_10 
