26 Flora of the Palonse Region 



solitary, ascending, spikelet-bearing above: glumes conspicuously ciliate on 

 the keels. Escaped from cultivation. 



46. POA. 



Inflorescence a contracted or open panicle: spikelets 2-6-flow- 

 ered, compressed, the rachilla usually glabrous: flowers perfect, 

 or rarely dioecious: empty glumes membranous, keeled, 1-3- 

 nerved: flowering glumes membranous, keeled, awnless, longer 

 than the empty ones, generally with a tuft of cobwebby hairs at 

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

 also the dorsal one; palet a little shorter than the flowering glumes, 

 2-nerved or 2-keeled: grain free, or sometimes adherent to the 

 palet. 



Annual. P. annua. 



Perennial. 



With running rootstocks. 



Culms terete. P. pratensis. 



Culms flattened. P. compressa. 



Without running rootstocks. 



Leaves filiform. P. filifoeia. 



Leaves broader. 



Leaves glaucous. P. nevadensis. 



Leaves not glaucous. P. sandbergii. 



P. annua L. Annual, the flattened culms 5-15 cm. tall: leaves glabrous, 

 the blades short and soft: panicle pyramidal, sometimes one-sided: spikelets 

 3-7-flowered, crowded, 4 mm. long: flowering glume 3-3.5 mm. long, hairy , 

 at base. In moist places becoming common. 



P. pratensis L. Perennial, with conspicuous running rootstocks, the 

 terete culms 30-90 cm. tall: panicle pyramidal, open, 6-20 cm. long, the as- 

 cending or spreading branches in whorls of 3-5, spikelet-bearing above the 

 middle: spikelets 3-5-flowered: flowering glume 3-5 mm. long, 5-nerved, 

 silky-pubescent on the midnerve and margins, cobwebby at the base. Every- 

 where introduced. 



P. compressa L. Usually low, spreading by rootstocks and forming dense 

 mats: the much flattened culms 15-30 cm. high, decumbent at base, glabrous: 

 panicle about 2 cm. long, contracted, the branches spikelet-bearing to the 

 base or nearly so: spikelets 3-9-flowered: flowering glume 3-nerved, the 

 nerves slightly pubescent below. Sparingly introduced. 



P. filifolia Vasey. Perennial, tufted: the slender culms 30-50 cm. tall: 

 leaves all filiform, involute, the numerous basal ones 10-20 cm. long, scab- 

 rous: panicle 6-8 cm. long, the ascending branches very slender, flexuous, 

 bearing 1-3 spikelets near the top: spikelets 7-10 mm. long, 2-5-flowered; 

 flowering glume compressed, 4-5 mm. long, 5-nerved, smooth or minutely 

 scabrid. Bluffs of Snake River near Lewiston. 



P. nevadensis Vasey. Tufted, pale and glaucous throughout: the stout 

 culms 60-90 cm. tall: basal leaves numerous, 30-40 cm. long, flat or involute, 

 smooth or nearly so; culm leaves 2: panicle erect, 10-20 cm. long, narrow, 

 dense, the appressed branches in half-whorls of 3-5, the shorter ones spike- 



