HITCHCOCK AND CHASE TEOPICAL NORTH AMEEICAN PANICUM. 461 



Blades linear, many times as long aa broad; spikelets 1.7 mm. 

 or more long. 

 First glume not over one-fourth the length of the spikelet, 

 truncate or triangular-tipped. 



See DicHOTOMiFLORA, p. 473. 

 First glume usually as much as half the length of the spike- 

 let, acute or acuminate See Capillaria, p. 476. 



Plants perennial. 

 Spikelets short-pediceled along one side of the panicle branches, forming 

 more or less spikelike racemes. 

 First glume nearly as long as the obtuse spikelets; plants with long wiry 



stolons with woolly nodes 111. P. obtusum. 



First glume much shorter than the spikelet. 

 Spikelets more or less hispid. 

 Sterile lemma glandless; second glume inflated-gibbous. 



73. P. ineptum. 

 Sterile lemrna bearing a pair of crateriform glands. 



See Stolonifera, p. 500. 

 Spikelets glabrous. 

 Blades lanceolate or ovate-lanceolate; glumes strongly carinate. 



See Stolonifera, p. 500. 

 Blades linear, often elongated; glumes not carinate or but slightly so. 



Fruit transversely rugose See Geminata, p. 465. 



Fruit not rugose. 

 Second glume shorter than the spikelet; fertile lemma subin- 

 durate, inroUed only at base, scabrous at the acute apex. 



112. P. stagnatile. 

 Second glume as long as the spikelet; fertile lemma indurate, 



inroUed to the summit See Laxa, p. 492. 



Spikelets in open or sometimes in contracted or congested panicles, but 

 not in 1-sided spikelike racemes. 



Fruit transversely rugose See Maxima, p. 483. 



Fruit not transversely rugose (minutely papillose-roughened in P. 

 millegrana). 

 Culms more or lesss succulent; plants glabrous or nearly so throughout, 

 aquatic or sub aquatic. 

 First glume not over one-fifth the length of the spikelet. 



See Dichotomiflora, p. 473. 

 First glume one-thuxl to half the length of the spikelet. 

 Fruit indurate, the margins of the lemma inrolled; culms erect; 



panicle contracted 48. P. condensum. 



Fruit subindurate, the margins of the lemma inrolled only at 

 base; culmp decumbent at base; panicles open. 

 Spikelets 1.8 mm. long; second glume shorter than the fruit; 



secondary panicle branches secund 112. P. stagnatile. 



Spikelets 2.5 mm. long; second glume exceeding the fruit; 



panicle branches not secimd 113. P. grande. 



Culms not succulent. 

 First glume hyaline, inconspicuous; spikelets acuminate; lower 



blades with long petiole-like bases 114. P. tuerckheimii. 



First glume evident. 

 First glume very small, not over one-fourth the length of the 

 small obovate, blunt, glabrous spikelets. 



See Parviglumia, p. 502. 



