No. 21. 
TRISETUM HALLII Scrib. 
Plant annual. 
Culms aaes not branching, geniculate, bolton: scabrous, 1 to 14 feet 
tall. 
Leaves; radical, few and small; of culm 3 or 4; sheaths usually exceeding 
internodes, open above, somewhat scabrous; blades flat or slightly involute, taper- 
pointed, scabrous on both sides, 1 to 14 lines wide, 3 to 5 inches long; ligule mem- 
branaceous, truncate, lacerate, 1 line long. 
Inflorescence a rather narrow, contracted, close, erect, or flexuous apical 4 to 
6 inches long, included or but slightly exserted; branches mostly in threes, slightly 
spreading, $ to 1 inch long, bearing pedicellate spikelets; crowded along their 
entire length. 
Spikelets obovate, 3- to 4-flowered, upper one sterile, small ae abortive, 2 to 
24 lines long; first glume narrowly inhebolate, acute, herbaceous, hispid on keel, 
3-nerved, + line wide, 2 lines long; second glume oblong-lanceolate, 5-nerved, twice 
as wide as the first; internode of rachilla slender, curved, articulate above, smooth, 
4 line long; floral glume lanceolate, with two attenuate teeth at apex, scarious, 
scabrid, 14 to’2 lines long, obscurely 3-nerved, mid-nerve excurrent in a slender 
awn 2 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; 6, empty glumes; c, floral glume; d, palet. 
This differs from T. interruptum Buckl. in its heavier panicle, shorter teeth of 
the flowering glume, and the higher insertion of the awn. Both species occur in 
Texas, 
