52 POACEAE. 



Bromus hordeaceus L. Annual, erect, 20-60 cm. tall; leaf blades pilose 

 or smooth, the sheaths pubescent with retrorse hairs; panicle narrow, dense, 

 5-10 cm. long; spikelets erect, 12-15 mm. long, 5-12-flowered; lemma pubes- 

 cent, bearing a stout straight or somewhat twisted awn 6-9 mm. long. 



Common in waste places; introduced from Europe. 



Bromus secalinus L. Chess or Cheat. Annual, erect, 30-70 cm. tall; 

 leaf blades 10-20 cm. long, sparsely hairy above, smooth beneath; sheaths 

 glabrous; panicle 8-18 cm. long, pyramidal, erect at first, in fruit somewhat 

 drooping; spikelets oblong-lanceolate, turgid in fruit, 10-18 mm. long; lemma 

 glabrous or nearly so, 6-8 mm. long, its margins involute in fruit, tipped with 

 an awn 2-5 mm. long; palea nearly equal to the lemma. 



Introduced from Europe. 



Bromus commutatus Schrad. Very similar to B. secalinus; panicle more 

 drooping; lemma broader, not inrolled in fruit, tipped with a stout straight 

 awn 7-8 mm. long. 



Introduced from Europe. 



79. DACTYLIS. 



Perennial grasses with flat leaves; inflorescence a densely 

 clustered or interrupted panicle; spikelets 3-5-flowered, short- 

 pedicelled, in small fascicles, the flowers all perfect or the upper 

 staminate; glumes thin, membranous, keeled, unequal, mucro- 

 nate; lemmas larger than the glumes, rigid, 5-nerved, keeled, 

 the midnerve extending into a point or short awn; palea shorter 

 than the lemma; grain free, enclosed in the lemma and palea. 



Dactylls glomerata L. Orchard-grass. Perennial, tufted, the stout stems 

 60-150 cm. tall; leaf blades flat, scabrous, 6-8 mm. broad; sheath scabrous, 

 exceeding the internode; panicle 3-10 cm. long, pyramidal-ovate, greenish or 

 purplish; branches solitary, ascending, spikelet-bearing above; lemmas con- 

 spicuously ciliate on the keels. 



Escaped from cultivation. 



80. POA. Blue-grass. 



Annual or perennial grasses wuth simple stems and narrow 

 usually flat leaves; inflorescence a contracted or open panicle, 

 spikelets 2-6-flowered, compressed, the rachilla usually glabrous; 

 flowers perfect or rarely dioecious; glumes membranous, keeled, 

 1-3-nerved; lemmas membranous, keeled, awnless, longer than 

 the glumes, generally with a tuft of cobwebby hairs at the base, 

 5-7-nerved, the marginal nerves usually pubescent, often also the 

 dorsal one; palea a little shorter than the lemma, 2-nerved or 

 2-keeled; grain free, or sometimes adherent to the palea. 



Annual; lemma without cobwebby hairs at base. P. annua. 



Perennial. 



Plants with creeping rootstocks. 



Stem flattened, 2-edged; panicles small. P. compressa. 



Stem cylindric. 



Lemma webbed, that is with a tuft of long hairs at 

 the base. 



