GRAMINEAE (GRASS FAMILY) 61 



33. TRISETUM Pers. OAT GRASS 



Tufted perennials (rarely annuals) with flat leaves and dense and spike- 

 like or narrow panicles. Spikelets 2 i-flowered, the flowers all perfect, or 

 the uppermost staminate; rachilla glabrous or pilose, extended beyond the 

 flowers. Glumes membranous, unequal, acute, persistent; lemmas 2 or more, 

 usually shorter than the glumes, deciduous, 2-toothed, bearing a dorsal awn 

 below the apex, or the lower one sometimes awnless; palet narrow, hyaline, 

 2-toothed. Stamens 3. Styles distinct; stigmas plumose. Grain free, inclosed 

 in the lemma. 



Panicle spike-like; first glume 3-nerved . . . . . 1. T. subspicatum. 



Panicle open; first glume 1-nerved 2. T. montanum. 



1. Trisetum subspicatum (L.) Beauv. Agrost. 180. 1812. Softly pubes- 

 cent to glabrous: stems simple, erect, 2-5 dm. high: sheaths shorter than the 

 internodes; leaves 3-10 cm. long, 2^1 mm. wide: panicle spike-like, 3-10 cm. 

 long, sometimes interrupted below; the rays erect: spikelets 2-3-flowered: 

 glumes hispid on the keel, shining; lemmas acuminate, scabrous; awn in- 

 serted below the sinus on the 2-toothed palet which it usually distinctly sur- 

 passes. Very common on mountain slopes in most parts of North America. 



2. Trisetum montanum Vasey, Bull. Torr. Bot. Club 13: 118. 1886. 

 Culms smooth, slender, 2-5 dm. high: leaves 12-25 cm. long, somewhat sca- 

 brous; lower sheaths pubescent: panicle loose and open but not spreading; rays 

 in fascicles of 5, unequal, 1-4 cm. long, suberect: spikelets 5 mm. long, 2- 

 flowered: glumes unequal; lemmas about 4 mm. long and surpassing the 

 glumes, acuminate and terminating in two short, fine setae, indistinctly 5- 

 nerved; palet narrow, bidentate. In the mountains from Colorado to New 

 Mexico. 



34. SCHEDONNARDUS Steud. CRAB GRASS 



Annual with branching culms, narrow leaves, and slender spikes arranged 

 along a common axis. Spikelets 1-flowered, sessile and alternate on the 

 rachis. Glumes narrow, membranous, acuminate; lemma longer, of similar 

 texture; palet narrow, snorter. Stamens 3. Styles distinct; stigmas plumose. 

 Grain linear, free, inclosed in the rigid lemma. 



1. Schedonnardus paniculatus (Nutt.) Trelease in Branner & Coville, 

 Kept. Geol. Surv. Ark. 18SS 4 : 236. 1891. Culms 20-45 cm. long, erect, slen- 

 der, rigid, branching at the base, scabrous: sheaths crowded at the base of the 

 culm, compressed, smooth and glabrous: leaves plane or folded, spirally 

 twisted, smooth, 5-8 cm. long, 2 mm. wide or less: spikes numerous, rigid, 

 widely spreading, alternate, the lower 5-10 cm. long, the axis and branches 

 triangular: spikelets 2.5-3 mm. long, sessile and appressed, alternate: glumes 

 hispid on the keel, the second longer than the first and exceeded by the acute 

 lemma. Dry prairies in the eastern part of our range, and south to Texas. 



36. AVENA L. TRUE OAT GRASS 



Annual or perennial grasses with flat leaves. Spikelets panicled, 1-2 or 

 sometimes numy-flowered; the lower perfect; the upper mostly staminate. 

 Glumes unequal; lemma 1 (rarely more), rounded on the back, mostly 5-11- 

 nerved, bearing a long, usually bent or twisted awn on the back or between 

 the two acute teeth at the apex. Stamens 3. Style short, distinct; the 

 stigmas plumose. Grain oblong-linear, deeply grooved, free but inclosed in 

 the palet. 



Annual 1. A. fatua. 



Perennial. 



Panicle open; the sriikelets on rather long capillary rays . . . 2. A. striata. 



Panicle narrow and spike-like . . . . . . . . 3. A. Mortoniana. 



