danthonia GRAMINE^E 743 



AVENA 



stems slender 1-2 feet high : leaves of sterile shoots with crowded sheaths 

 and narrow involute blades, sparsely pilose to glabrous, 4-12 inches long : 

 sheaths of the stem shorter than the internodes, more or less pilose : 

 ligules short, ciliate: inflorescence a short spicate panicle of 3-12 erect 

 spikelets: empty glumes lanceolate, acute or acuminate, keeled, smooth, 

 4-5 lines long, exceeding the flowering glumes which are broadly lanceolate, 

 2-3 lines long, acutish, 2-toothed, the awn more or less bent and twisted, 

 4-6 lines long. On low prairies, eastern Washington to southern California 

 Montana and Canada. 



Var. Cusickii Williams. Larger: leaves longer flatter, softer, less 

 scabrous, quite destitute of pubescence, rather large spikelets and usually 

 more open panicle. In the Blue Mountains of Oregon. 



1). unispicata Munro. Stems loosely tufted, 6-12 inches high : sheaths 

 shorter than the internodes, or the lower ones longer, pubescent with long 

 white hairs : ligules very short or reduced to a row of white hairs : leaves 

 flat or more or less involute with acuminate tips, 2-4 inches long, more or 

 less pubescent: inflorescence a single terminal spikelet: empty glumes lan- 

 ceolate, long-acuminate, exceeding the upper flowering one, glabrous, 6-12 

 lines long: flowering glumes lanceolate, acute, 4-5 lines long, termina- 

 ting in 2 usually dark-colored awns, ciliate on the margins : central awn 

 twisted and bent below the middle, about 6 lines long. In partially barren 

 places, eastern Washington to California. 



D. Americana Scribn. U. S. Dept. Agr. Cir. 30, 5. A slender dense- 

 ly cespitose perennial 8-16 inches high, with short slightly inflated sheaths, 

 narrow mostly involute leaves and simple panicles of 1-4 large spikelets: 

 sheaths much shorter than the internodes, pubescent, at least the lower 

 ones long-bearded at the throat: empty glumes acuminate-lanceolate the 

 narrowed apex obtuse, 6-9 lines long, as long as or slightly exceeding the 

 flowers : flowering glumes S-4 lines long, rounded and glabrous on the back, 

 densely silky villous on the margins from just above the base to a little 

 above the middle, abruptly 2-toothed, the teeth very slender bristles 2-3 

 lines long: awn very slender twisted below, 3-5 lines long. Brit. Columbia 

 to California and Chile. 



27 AVENA L. Sp. 76. 



Annual or perennial grasses with usually flat leaves and nam- 

 erous spikelets in panicles. Spikelets one- to several-flowered, 

 the lower flowers perfect, the upper often staminate or imperfect. 

 Glumes 3 to several the 2 outer empty, somewhat unequal, mem- 

 branous, persistent. Flowering glumes deciduous, rounded on 

 the back, acute, generally bearing a dorsal awn, the apex often 

 2-toothed. Palet narrow, 2-toothed. Stamens 3. Styles short, 

 distinct, with plumose stigmas. Grain oblong, deeply furrowed, 

 enclosed in the glume and palet, free or sometimes attached to 

 the palet. 



A. fatua L. Sp. 80. Stems stout, 1-4 feet high, erect, smooth : sheaths, 

 smooth, or scabrous at the summit, sometimes sparingly hirsute, the lower 

 often longer than the internodes: ligules 1-2 lines long: leaves 3-8 inches 

 long, 1-4 lines wide: panicle open 4-12 inches long, the branches ascend- 

 ing : spikelets 2-4 flowered, drooping : empty glumes 9-12 lines long, smooth, 

 flowering glumes 6-9 lines long, with a ring of stiff brown hairs at base, 

 pubescent with long rigid brown hairs, bearing, a long bent and twisted 

 awn. In fields and waste places : naturalized from Europe. 



Var. glabrescens Coss. Stems stout, pale, \%-2% feet high : sheaths 

 equalling the internodes : leaves flat, 4-6 inches wide : flowering glumes 



