No. 21. 

 TRISETUM HALLII Scrib. 



Plant .annual. 



Culms slender, not branching, geniculate, ascending, scabrous, 1 to \\ feet 

 tall. 



Leaves; radical, few and small; of culm 3 or 4; slieaths usually exceeding 

 internodes, oi^en above, somewhat scabrous: blades flat or slightly involute, taper- 

 pointed, scabrous on both sides, 1 to 1^ lines wide, 3 to 5 inches long; ligule mem- 

 branaceous, truncate, lacerate, 1 line long. 



Inflorescence a rather narrow, contracted, close, erect, uv flexuous panicle, 4 to 

 inches long, included or but slightly exserted; branches mostly in tlirees, slightly 

 spreading, ^ to 1 inch long, bearing pedicellate spikelets; crowded along their 

 entire length. 



Spikelets obovate, .'5- to 4-flowered, upper one sterile, small and aljortive, 2 to 

 3^- lines long; first glume narrowly lanceolate, acute, herbaceous, hispid on keel, 

 ;3-nerved, I line wide, 2 lines long; second glume oblong-lanceolate, 5-nerved, twice 

 as wide astlie fii-st; internode of rachiUa slender, curved, articulate above, smooth, 

 Y line long; floral glume lanceolate, with two attenuate teeth at apex, scarious, 

 scabrid, 1^ to 2 lines long, obscurely 3-nerved, mid-nerve excuri-ent in a slendei* 

 awn ^ to 4 lines long; palet narrowly linear, lanceolate when spread out, thin, 

 2-keeled, 1 line long, not inclosed in floral glume. 



Grains, none found in the specimens examined 



Plate XXI: a, spikelet; h. empty glumes; c, floral glume; d, palet. 



This diff^ers from T. iiitervn ptiiin Buckl. in its lieavier panicle, shorter teeth of 

 tlie flowering glume, and the liigher insertion of the awn. Both species occur in 

 Texas. 



