GRAMINEAE (GEASS FAMILY) 61 



33. TRISETUM Pers. Oat Grass 



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

 like or narrow panicles. Spikelets 2-4-flowered, the flowers all perfect, or 

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

 flowers. Glumes hiembranous, 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. euhspicatum. 



Panicle open; first glume 1-nerved , 2. Ti 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, 2-4 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, shorter. Stamens 3. Styles distinct; stigmas plumose. 

 Grain linear, free, inclosed in the rigid lemma. 



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

 Rept. Geol. Surv. Ark. 1888*: 236. 1891. Cuhns 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, 



35. AVENA L. True Oat Grass 



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

 sometimes many-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 shortj distinct; the 

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

 the palet. 



Annual . . 1. A. fatua. 



Perennial. 



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



PaniMe narrow anrrspik*»-1ikc . . . . ^,^ . ,3. A. ATortnnian.^. 



