Oat Tribe 39 



flowered ; both flowers perfect, the hairy rachilla ex- 

 tended beyond or rarely terminated by a staminate one. 

 Glumes 4, the 2 outer empty, keeled, acute, membranous, 

 shining, persistent ; the flowering glumes similar in tex- 

 ture, deciduous, bearing a dorsal awn, toothed at the 

 apex. Palea narrow. Stamens 3. Styles distinct. 

 Grain oblong, free and enclosed in the glume. 



1. D. calycina Presl. Annual; culms slender, 1-6 dm. high; 

 sheaths smooth; leaves few, 3-6 cm. long, 1 mm. wide or less; 

 panicle spreading, about % the length of the culms, bearing 1-5 

 spikelets above the middle, the lowest of which are on spreading 

 pedicels; spikelets 2-flowered; empty glumes about 2 mm. long, 

 hairy below, shining above, 5-nerved, emarginate with 4 minute 

 ciliate teeth ; awn inserted below the middle, about 6 mm. long, 

 bent near the middle and twisted below. 



Occasional on dry mesas or in open places in the foothills and mountains. 



21. AVENA L. OAT. 



Annual or perennial grasses with generally flat leaves 

 and paniculate inflorescence. Spikelets 2-several-flower- 

 ed or rarely 1 -flowered ; the lower flowers perfect, the 

 upper usually staminate. Glumes 4-many, the 2 outer 

 empty, somewhat unequal, membranous, persistent ; 

 flowering glumes deciduous, rounded on the back, acute, 

 generally bearing a dorsal awn, apex often 2-toothed. 

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

 distinct. Grain oblong, deeply furrowed, enclosed in 

 the glume and palea, free or sometimes adherent to the 

 latter. 



1. A. fatua L. (WILD OAT.) Culms usually tufted, 5-15 dm. 

 high; leaves scabrid, rather long and broad; panicle 1-4 dm. 

 long, its branches unequal, long filiform ; spikelets drooping, 2-3- 

 flowered ; empty glumes subequal, ovate-lanceolate, 20-25 mm. 

 long, 9-11-nerved; flowering glumes 18 mm. long, acute, bifid, 

 yellowish hairy especially below, 9-nerved; awn from near the 



