

POACEAE. 



nikdetfl 2-6-flowcred, compressed, the rachilla usually glabrous, 



, (U , fed or rarely dioecious; glumes membranous, keeled, 



t;,,l; lemmas membranous, keeled awnless, longer than 



hi- h,„Hs. generally with a tuft of cobwebby hairs at the base, 



V-7-n rv.-.l Marginal nerves usually pubescent, often also the 



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



eled; grain free, or sometimes adherent to the palea. 



Annual; lemma without cobwebby hairs at base. 



1'. nnni.ils. 



Plants with creeping rootstocks. 



ma . .impressed, 2-edged; panicles small, 

 ms cylindric. . 



Lemma webbed, that is with a tuft of hairs at base. 

 Lemma without a tuft of hairs at base. 

 nts tufted, without rootstocks. 

 Web present at base of lemma. 



Panicle close; leaf blades flat, thin and lax. 

 Panicle open; leaf blades narrow, not thin and lax. 

 Ligule 3-5 mm. long; panicle loose, somewhat 



drooping, 10-30 cm. long. 

 Ligule very short; panicle erect, 4-10 cm. long. 

 Web absent from base of lemma. 



Stems coarse and tall, 60-100 cm. high. 



Leaves narrow, pale, involute; panicle narrow, 



erect. 

 Leaves flat, rarely involute, green or rarely 



glaucescent; panicle ample. 

 OS not coarse or tall, usually less than 60 cm. 



tall. 

 Leaves flat or folded, not filiform. 



Lemmas pubescent at base; leaves 1 mm. 



broad, usually folded. 

 Lemmas puberulent at base; leaves 2 mm. 

 broad, usually flat. 

 Leaves involute and filiform. 

 Llorets close; ligule long. 

 1 lorets loose; ligule short. 



P. annua. 



P. compressa. 



P. pratensis. 

 P. olneyae. 



P. bolanderi. 



P. Iriflora. 

 P. nemoralis. 



P. brachyglossa. 

 P. ampla. 



P. sandbergii. 



P. saxalilis. 



P. idahoensis. 

 P. capillar tfolia. 



Poa annua L. A nnual Bluegrass. Annual, the compressed stems 5—15 cm. 



tall; I labrous, the blades short and soft; panicle pyramidal, sometimes 



1; spikeleta 3-7-flowered, crowded, 4 mm. long; lemma 3-3.5 mm. long, 



MM litirv at base. In moist places becoming common, apparently native 



in the foothills. 



Poa compressa L. Canada Bluegrass. Usually low, spreading by root- 



■ I forming dense mats; the much compressed stems 15-40 cm. high, 



mbcnl al Jabrous; panicle 3-7 cm. long, contracted, the branches 



■pikelet-bearing to the base or nearly so; spikelets 3-9-flowered; lemmas ob- 



curel; I, the nerves slightly pubescent below. Sparingly introduced. 



Poa pratensis L. Kentucky Bluegrass. Perennial, with conspicuous run- 



< ks, the terete stems 30-90 cm. tall; panicle pyramidal, open, 



ending or spreading branches in whorls of 3-5, spikelet- 



the middle; Bpikelets 3-5-flowered; lemmas 3-5 mm. long with 



intermediate nerves, silky-pubescent on the midnerve and margins, 



->:. Everywhere introduced. 



