322 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



a feathery panicle, the small narrow spikelets margined with silky white hairs 

 to 8 mm. long, the general appearance unlike that of any other species of 

 Paspalum. 



Banks and steep slopes, Costa Rica and the Lesser Antilles to northern South 

 America. Originally described from St. Christopher. Paspalum saccharoides 

 was described from the West Indies. Moenchia speciosa was based on Panicum 

 saccharoides. 



Guadeloupe, Dominica, Martinique, Grenada, Trinidad, and Tobago. 



36. PANICUM L. 



Inflorescence paniculate (rarely racemose) ; spikelets pedicellate, biconvex; 

 first glume present ; sterile lemma usually inclosing a hyaline palea, sometimes 

 a staminate flower ; fruit chartaceous-indurate, the margins of the lemma in- 

 rolled. 



The North American species of this genus have been described in two earlier 

 papers* in which a detailed citation of specimens is given. In the present 

 paper there is given only a resumg collated from these two papers. 



Axis of branchlets produced beyond the base of the uppermost spikelet as a 

 point or bristle 1 to 6 mm. long. (Subgenus Paurochaetium.) 

 First glume rounded or truncate ; second glume about as long as fruit. 



3. P. chapmani. 

 First glume acute ; second glume about two-thirds as long as fruit. 



Spikelets 1.5 mm. long; blades involute 1. P. distantiflonim. 



Spikelets 2 mm. long; blades flat 2. P. utowanaeum. 



Axis of branchlets not produced into a bristle. (In P. geminatum the somewhat 

 flattened axis pointed but not bristle-form.) 

 Basal leaves usually distinctly different from those of the culm, forming a 

 winter rosette ; culms at first simple, the spikelets of the primary panicle 

 not perfecting seed, later usually becoming much branched, the small 

 secondary panicles with cleistogamous fruitful spikelets. Mostly delicate 

 grasses with small open primary panicles (narrow in P. ncuranthum and 

 P. caerulescens) , the small elliptical or obovate, obtuse spikelets (pointed 

 in P. fusiforme) on capillary, often flexuous pedicels. (Subgenus Di- 



CHANTHELIUM. ) 



Foliage soft and lax, the flat blades prominently ciliate ; plants branching 

 from the base, finally forming rosettes or cushions. (Laxifloka.) 



Spikelets papillose-pilose ; sheaths retrorsely pilose 50. P. xalapense. 



Spikelets glabrous ; sheaths not retrorsely pilose. 



Blades glabrous on the surface 51. P. polycaulon. 



Blades pilose on the surface 52. P. strigosum^. 



Foliage not soft and lax ; plants branching from the culm nodes, 



Spikelets glabrous ; plants glabrous throughout ; autumnal phase erect, 

 not bushy-branching. (Dichotoma in part.) 

 Plants delicate, tufted, not over 25 cm. tall ; spikelets 1.2 mm. long. 



67. P. chamaelonche. 

 Plants slender but not delicate, usually at least 50 cm. tall ; spikelets 

 1.6 mm. long or more. 

 Spikelets not over 1.6 mm. long ; panicles narrow ; plants glaucous 



bluish green 60. P. caerulescens. 



Spikelets 2 mm. or more long; panicles open 60. P. roanakense. 



*Contr. U. S. Nat. Herb. 15: 1910; 17: 459-539. 1915. 



