54 POACEAE. 



Poa annua L. Annual Blue-grass. Annual, the compressed stems 5-15 

 cm. tall; leaves glabrous, the blades short and soft; panicle pyramidal, some- 

 times 1-sided; spikelets 3-7-flowered, crowded, 4 mm. long; lemma 3-3.5 mm. 

 long, not hairy at base. 



Introduced; common along waysides and in cultivated ground. 



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

 stocks and forming dense mats, the much compressed stems 15-40 cm. high, 

 decumbent at base, glabrous; panicle 3-7 cm. long, contracted, the branches 

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

 scurely nerved, the nerves slightly pubescent below. 



Sparingly introduced. 



Poa macrantha Vasey. Pale green; rootstocks extensively creeping, stout; 

 leaves involute or folded; panicle 5-10 cm. long; staminate spikelets yellowish, 

 10-15 mm. long; pistillate smaller. 



Common in sand dunes along the coast. 



Poa pratensis L. Kentucky Blue-grass. Perennial with conspicuous run- 

 ning rootstocks, the terete stems 30-90 cm. tall; panicle pyramidal, open, 

 6-20 cm. long, the ascending or spreading branches in whorls of 3-5, spikelet- 

 bearing above the middle; spikelets 3-5-flowered; lemmas 3-5 mm. long with 

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

 cobwebby at the base. 



Meadows and pastures everywhere. 



Poa confinis Vasey. Stems 5-15 cm. high; leaves numerous, very narrow, 

 involute; panicle 1-3 cm. long, the short branches in pairs; spikelets 3-5- 

 flowered; lemmas broadly ovate. 



High sea beaches; common on the ocean coast. 



Poa nervosa (Hook.) Vasey. Stems weak, 30-40 cm. high; leaves soft, 

 green, flat or folded; panicle lax, 6-10 cm. long; spikelets pale green, compressed, 

 the 4-7 florets distant; lemma thin, lanceolate, scabrous. 



On moist wooded banks, rare. Nootka Sound, British Columbia, Scouler; 

 Cape Horn, Washington, Piper; Multnomah Falls, Oregon, Piper. 



Poa trivialis L. Rough Meadow-grass. Stems 30-60 cm. high; sheaths 

 and fiat blades scabrous; ligule well developed; panicle rather loose; spikelets 

 mostly 3-flowered; lemma 5-nerved, the nerves very prominent. 



Sparingly introduced. 



Poa arctica R. Br. Perennial by creeping rootstocks; stems slender, 

 2-3-jointed, erect, 10-30 cm. high; leaves green, flat or folded, 2-5 cm. long, 

 2-3 mm. wide; panicle loose, pyramidal, erect or somewhat nodding, 3-8 cm. 

 long, the slender rays mostly in twos; spikelets oblong-obovate, 3-6-flowered, 

 6-7 mm. long; glumes ovate, acute, subequal; lemma purplish, ovate, ob- 

 tusish, pubescent on the keel and lateral nerves below the middle, 3-4 mm. 

 long, the tuft of hairs at base nearly as long. 



Mount Rainier, Piper, Allen; our form is not typical and has been mistaken 

 for P. laxa Haenke. 



Poa triflora Gilib. Fowl Meadow-grass. Tufted, the stems 60-90 cm. high; 

 leaves narrow, linear, smooth and soft; ligule conspicuous; panicle usually 

 purple, 10-30 cm. long, the branches mostly in fives; spikelets 2-5-flowered ; 

 lemma obscurely nerved. 



In wet places, common. 



Poa leptocoma Bong. Glabrous, bright green; stems slender, erect, 

 20-40 cm. high; leaves flat, flaccid, 5-12 cm. long, 3-4 mm. wide; panicle lax, 

 5-10 cm. long, more or less nodding, the capillary branches mostly in twos 



