22 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Panicles narrow and few-flowered; culms 

 erect and wiry; blades drying in- 

 volute See Tenera, p. 97. 



Panicles open or contracted, many- 

 flowered. 

 Panicles 40 to 60 cm. long, the numer- 

 ous elongated branches in verticils; 



tropical species 81. P. megiston. 



Panicles mostly much less than 40 cm. 

 long; branches not verticillate. 

 Spikelets short-pediceled along the 



nearly simple panicle branches .See Agrostoidia, 



p. 99. 

 Spikelets long-pediceled; panicle 

 open (dense in P. Mrsutum). 

 Spikelets viscid ; first glume about 

 as long as the second; tropical 



species 79. P. glutinosum. 



Spikelets not viscid; first glume 

 much shorter than the second. 

 Culms erect or rarely spreading; 

 blades linear, usually elon- 

 gated; spikelets pointed. .See Diffusa, p. 71. 

 Culms decumbent at base; 

 blades ovate to oblong-lan- 

 ceolate; spikelets blunt; 

 tropical species. 

 Panicles mostly less than 5 



cm. long; plants glaucous. 77. P. parvifolium. 

 Panicles 10 to 20 cm. long; 



plants not glaucous 78. P. millegrana. 



Subgenus PAUROCHAETIUM subgen. nov. 



Perennials; culms tufted, erect, blades not over 7 mm. wide; inflorescence narrow, 

 more or less interrupted, the branches short and appressed, the ultimate branchlets 

 bearing 1 to several spikelets, produced beyond the uppermost spikelet as a bristle 1 to 

 6 mm. long; spikelets 1.5 to 3.5 mm. long, much swollen on the face, glabrous; fruit 

 transversely rugose, apiculate. 

 The type species is P. distantifiorum Michx. 



This group approaches Chaetochloa in having branchlets produced into bristles, and 

 in the shape of the spikelets and rugose fruits. 

 Blades elongated, usually more than 15 cm. long, narrowed 

 toward the base. 



Spikelets about 3.5 mm. long 5. P. reverchoni. 



Spikelets about 2 mm. long, or less. 



First glume rounded or truncate; second glume about 



as long as fruit 3. P. chapmani. 



