62 POACEAE 



Empty glumes longer than the flowers; panicle narrow and spike-like, strict; plant 



tufted. 



Plant 11.5 dm. high; leaves strongly involute; callus of the lemma and prolonga- 

 tion of the rachilla long-hairy. 2. A. M or toniana. 

 Plant 2-4 dm. high; leaves mostly flat; callus and rachilla short-hairy. 



3. A. Hookeri. 



Annuals; panicle open; empty glumes over 2 cm. long; spikelets 2-4-flowered. 

 Lemma hairy, at least at the base; awn strongly twisted. 4. A. fatua. 



Lemma glabrous; awn scarcely twisted. 5. A. sativa. 



1. A. striata Michx. Stem 3-6 dm. high, glabrous; leaf-blades 2-15 cm. 

 long, 3-6 mm. wide, scabrous above; panicle 7-12 cm. long; spikelets 3-6-flowered; 

 empty glumes glabrous, the first 5-7 mm. long, 1-nerved, the second 6-8 mm. 

 long, 3-nerved; lemma 7-9 mm. long; awn 8-10 mm. long. In woods: N.B. 

 Pa. N.M. B.C. Mont.Subalp. Je-Au. 



2. A. Mortoniana Scribn. Stem erect, 1-1.5 dm. high, glabrous, striate; 

 leaf-blades 5-15 cm. long, 2 mm. wide or less, rigid, convolute, glabrous on both 

 sides or pubescent above; panicle 2-4 cm. long; spikelets about 1 cm. long, 2- 

 flowered; the first glume 1-nerved, the second 3-nerved; lemma 8-9 mm. long, 

 glabrous; awn 7-8 mm. long, twisted below and geniculate. Mountain tops: 

 Colo. Alp. 



3. A. Hookeri Scribn. Stem 3-6 dm. high; leaf-blades flat, firm, 5-15 cm. 

 long, 1.5-3 mm. wide, glabrous, scabrous on the margins; panicle 8-12 cm. long; 

 spikelets 12-17 mm. long, 3-6-flowered; empty glumes about 1 cm. long, thin, 

 greenish; lemma about 8 mm. long, brownish; awn over 1 cm. long, bent and 

 twisted. A. americana Scribn. Ridges and hillsides: Sask. S.D. Colo. 

 Alta. Submont. Mont. Je-Jl. 



4. A. fatua L. Annual; stem 3-12 dm. high, stout, glabrous; leaf-blades 

 flat, 1-3 dm. long, 5-15 mm. wide; panicle open, 1-3 dm. long; empty glumes 2- 

 2.5 cm. long, smooth; lemma 12-18 mm. long, in the typical form covered with 

 long brown hairs; awn 2-2.5 cm. long. WILD OATS. A variety with lemma 

 glabrous except at the base is A. fatua glabrata Peterm. Fields and waste places: 

 Sask. Wis. Mo. -N.M. Calif. B.C.; native of Eurasia and established as 

 a weed in grain fields. Plain Submont. 



5. A. sativa L. Erect annual, closely resembling the preceding; stem 

 glabrous, 6-12 dm. high; panicle open, 1-3 dm. long, usually with drooping spike- 

 lets; empty glumes 2-3 cm. long, glabrous; lemma 15-20 mm. long, glabrous; 

 awn 2-3 cm. long. OATS. Occasionally escaped and established: Me. -Fla. 

 Tex. Yukon. My-S. 



37. ARRHENATHERUM Beativ. OAT-GRASS. 



Tall perennials. Inflorescence paniculate. Spikelets 2-flowered, the lower 

 flower staminate, the upper one perfect or pistillate, the rachilla articulated 

 above the empty glumes and prolonged beyond the flowers. Empty glumes 2, 

 persistent, thin-membranous, keeled. Lemma more rigid, somewhat toothed at 

 the apex, that of the lower flower bearing near the base a long dorsal twisted 

 and geniculate awn, that of the upper one awnless, or short-awned below the 

 apex. Palet 2-keeled, hyaline, narrow. Stamens 3. Styles short, distinct; stig- 

 mas plumose. Grain hardly sulcate. 



1. A. elatius (L.) Beauv. Perennial, with a cespitose rootstock; stem 

 glabrous, 6-12 dm. high, erect; leaf -blades flat, 5-30 cm. long, 2-8 mm. wide, 

 scabrous; panicle 1-3 dm. long, narrow, with erect blanches; lemmas about 8 

 mm. long, that of the lower flower with a bent and twisted awn about 1 cm. 

 long. Fields and waste places: Me. Ga. Calif. B.C.; nat. from Eu. Je-Jl. 



38. DANTHONIA DC. WILD OAT-GRASS. 



Usually perennial, all ours cespitose. Inflorescence a contracted or open 

 diffuse panicle. Ligules usually represented by a hairy ring. Spikelets 3-many- 

 flowered, the flowers perfect or the upper ones staminate, the rachilla pilose, 

 articulated between the glumes and prolonged beyond them. Empty glumes 2, 

 persistent, usually extending beyond the lemma, keeled, acute or acuminate. 



