ARISTIDA BROMUS 345 



2. Lower glume about ^ as long as the upper 



a. Central awn 1-3.5 in. long A. purpurea 



b. Central awn 8-15 mm. long A.fasciculdta 



AVENA Linne 1753 OAT 



(Lat. name of the oat) 



PL 46, fig. 8. 



Spikelets 2-several-flowered, in panicles, the upper flower often stamin- 

 ate and imperfect; glumes more or less equal, persistent, often large and 

 enclosing the spikelet; lemma rounded on the back, acute, usually awned 

 on the back, the apex often 2-toothed, palet narrow, 2-toothed; annual or 

 perennial. 



1. Glumes 1-2 cm. long, enclosing the spikelet; an- 



nual A.fdtua 



2. Glumes 4-7 mm. long, much shorter than the 



spikelet; perennial 



a. Lemma 6-8 mm. long ; panicle open A. stridta 



b. Lemma 12 mm. long; panicle spike-like A.mortonidna 



BECKMANNIA Host 1805 



(Named for Beckmann, a Russian botanist) 



PL 46, fig. 5. 



Spikelets 1-2-flowered, globose, compressed, densely imbricated in 2 

 rows on one side of a continuous axis, in short 1 -sided spikes ; glumes sack- 

 like; lemma narrow, papery, palet 2-keeled ; perennial with erect spikes in 

 a terminal panicle. 



Stems 1.5-3 ft. high; spikes 10-12 mm. long; spikelets 

 2-3 mm. long B.eruciformis 



BROMUS Linne 1753 .BROME GRASS, CHESS 



(Gr. bromos, a kind of oats) 



PL 45, fig. 18. 



Spikelets 5-12-flowered, in terminal panicles; glumes unequal, acute; 

 lemma rounded or keeled, 5-9-nerved, apex usually 2-toothed and with an 

 awn just below the summit, palet shorter, 2-keeled; annual or perennial. 

 1. Annual weeds 

 a. Lemma awned 



(1) Spikelets 5-8-flowered, hanging; lemma 8- 



12 mm. long, the awn 12-16 mm. long B. tectorum 



