No. 22. 

 TRISETUM INTERRUPTUM Biickley. 



Plant slender, tufted, annual, rather glaucous throughout. 



Roots numerous, tine. 



Culms ascending, geniculate, bi'anching, terete, smooth, (J to l.S inches tall. 



ieaws of radical shoots numerous, with smooth or cinerous-i5ube.scent.sheatlis 

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

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

 flat or involute, scabrous, 3 to 3 inches long; ligule membranaceous, l9,cerate, 

 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, i to 1 inch long. 



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

 tive, 2 to 2^ lines long; first glume oblauceolate, acute, herbaceous, hispid on 

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

 5-nerved; internode of rachilla curved, glabrous, 4 line long; floral glume lanceo- 

 late, rounded on back, scarious above, rigid, smooth, about 3 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, 3 to 3 lines long; palet narrowly 

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

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



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



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

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



Abundant in Texas. 



