No. 22. 

 TRISETUM INTERRUPTUM Buckley. 



Plant slender, tufted, annual, rather glaucous throughout. 



Boots numerous, fine. 



Culms ascending, geniculate, branching, terete, smooth, 6 to 18 inches tall. 



Leaves of radical shoots numerous, with smooth or cinerous-pubescent sheaths 

 and flat blades, hispid above, 2 to 3 inches long; of culm 3 to 5; sheaths usually 

 little shorter than internodes, smooth or somewhat scabrous or pubescent; blades 

 flat or involute, scabrous, 2 to 3 inches long; ligule membranaceous, lacerate, 

 obliquely truncate, 1 line long. 



Inflorescence a narrow, somewhat interrupted, erect or flexuous panicle, 3 to 

 5 inches long; branches in 2's or 3's of unequal length, \ to 1 inch long. 



Spilcelets sessile, obovate, 3- to 4-flowered, upper one sterile or small and abor- 

 tive, 2 to 2i lines long; first glume oblanceolate, acute, berbaceoiis, hispid on 

 keel, 3-nerved, 1| to 2 lines long; second glume same, but twice as wide and 

 5-nerved; internode of rachilla curved, glabrous, \ line long; floral glume lanceo- 

 late, rounded on back, scarious above, rigid, smooth, about 2 lines long, 3-nerved, 

 ending in 2 slender teeth, 2 lateral nerves uniting above with the midnerve and 

 forming above the middle a slender hispid awn, 2 to 3 lines long; palet narrowly 

 linear, wider at top, lanceolate when spread out, thin, smooth, 2-keeled, cleft at 

 apex, standing out of floral glume, 1 line long. 



Grain yellowish, opaque, elliptical, flattened, 1 line long. 



Plate XXII; a, floral glume, side view; b, palet; c, spikelet; d (marked a in 

 plate), empty glumes. The floral glume, a, is not well figured. 



Abundant in Texas. 



