130 POACEAE 



long, its branches ascending or erect, somewliat tlexuous, naked below : spikelets 3-4- 



flowered, tiie first empty scale about i as long as the second which is about 5 mm. long, the 



flowering scales 5-0 mm. long, hisi)idulous, e;ich bearing a long, bent and twisted awn. 



In waste places find fields, Missouri. Iviinsiis and Mississippi. Xaturalized from Europe or Asia. 

 Summer. 



3. Trisetum Hallii Scribn. Stems tufted, 1.5-o dm. tall, slender: leaf-blades 3-13 

 cm. long, 2-3 mm. witle, rough, flat, or somewiiat involute : panicle contracted, 3-15 cm. 

 long, its branches erect or nearly so : spikelets 4-5 mm. long, exclusive of the awns, the 

 first scale nuich narrower and almost as long as tlie second. 



On prairies, Texas. Spring. 



4. Trisetum internipttim Buckl. Stems tufted, 5 dm. tall or less, slender : leaf- 

 sheaths glabrous or pnlx'scent ; blades tlat or involute, rough, 8 cm. long or less, 1-2 mm. 

 wide : panicle 4-13 cm. long, its l)ranches erect or nearly so : spikelets 4-5 mm. long, ex- 

 clusive of the awns, tlie first scale narrower than the second but about as long. 



In dry soil, Texas. Spring. 



5. Trisetum aristatvim (Scribn. ik Afer. ) Nasli. Stems 4-6 dm. tall, erect, slen- 

 der: leaf-blades 1.5 dm. long or less, 1-2 mm. wide, roughish : panicle slender, 1.5-2.5 

 dm. long, its branches erect or nearly so, the larger ones 6-8 cm. long : spikelets of 4 or 5 

 scales, 4.5-5 mm. long, exclusive of the awns, the first scale linear, .several times narrower 

 than the broad secf)nd scale. 



In moist or dry soil, North Carolina. Summer. 



6. Trisetum Pennsylvanicum ( L. ) B. S. I*. Stems 3-9 dm. tall, erect, slender and 

 often weak : leaf-siieaths sometimes rough ; blades 1 dm. long or le.ss, 1-4 mm. wide, 

 rough: panicle 6-15 cm. long, its branches erector ascending: spikelets of four scales, 

 the empty ones about equal, the first a little shorter than the second, the flowering scales 

 4-5 mm. long, the second one hispidulous or nearly glabrous. [T. palustre Torr.] 



In swamps and wot meadows, Xew York to Virginia, Tennessee and Florida. Spring and summer. 



7. Trisetum Ludovicianiun N'asey. Stems 6-9 dm. long, weak : leaf-blades flat, the 

 larger ones 1.5-2 dm. long, 4-6 mm. wide, rough: panicle 1.5-2.5 dm. long, its branches 

 erect or nearly so : spikelets usually of 4 scales, the first a little shorter than the second, 

 the second flowering scale strongly his))idulous. 



In wet places, Louisiana. Spring. 



72. AVENA L. 



Annual or perennial grasses, varying in habit, with usually flat leaf-blades and terminal 

 contracted or open panicles. Spikelets generally large, erect or pendulous, usually 2- 

 several-flowered, rarely 1-flowered, the rachilla articulated between the fertile flowers, the 

 lower flowers perfect, the upper ones often staminate or wanting. Scales 4-several, rarely 

 3, the 2 outer empty, membranous, exceeding or shorter than the flowering scales, persist- 

 ent ; the flowering scales 5-9-nerved, I'ounded on the back, the apex frequently shortly 2- 

 toothed, the scales enclosing perfect flowers and bearing a dorsal twisted geniculate awn^ 

 the upper empty ones or those infolding staminate flowers awnless ; palet 2-cleft or 2- 

 toothed, narrow. Stamens 3. Styles distinct. Grain deeply furrowed, usually pubescent. 



1. Avena sativa L. Annual. Stems 8-15 dm. tall : leaf-blades flat, 2.5 dm. long 

 or less, 5-10 mm. wide or more : panicle usually 1.5-4 dm. long, its branches erect or ascend- 

 ing : empty scales of the spikelet 2-3 cm. long, acuminate, the flowering ones shorter, 

 awned or awnless. 



In fields and waste places, escaped from cidtivation nearly every where in civilized North America 

 Summer. 0.\t. 



73. ARRHENATHERUM Heauv. 

 Tall jierennial gra.sses, with flat leaf-blades and terminal open or contracted panicles. 

 Spikelets 2-flowered, the lower flower staminate, the U])per one perfect orpistillate, the rachilla 

 articulated above the empty scales and prolonged beyond the flowers. Scales 4, the 2 outer 

 empty, persistent, thin-membranous, keeled, the flowering scales more rigid, somewhat 

 toothed at the apex, the lower one bearing near the base a long dorsal twisted and genicu- 

 late awn, the upjjcr scale awnless, or sliort -awned below the apex ; palet 2-keeled, hyaline, 

 narrow. Stamens 3. Styles short, distinct. Stigmas plumose. Grain hardly sulcate. 



1. Arrhenatherum el^tius (L. ) Beauv. Stems 6-12 dm. tall, erect: leaf-blades 

 6-30 cm. long, 2-8 nun. wide, rough : panicle 1-3 dm. long, its branches erect : em]ity 



