70 GBAMINEAE (GRASS FAMILY) 



second one; lemma 2.5-3 mm. long, distinctly 5-nerved, the nerves pilose be- 

 low. — More or less frequent in waste and cvdtiyated grounds throughout 

 North America. 



2. Poa compressa L. Sp. PL 69. 1753. Pale bluish-green, glabrous: culms 

 1.5-6 dm. tall, decumbent at the base, from long horizontal rootstocks, much 

 flattened: sheaths loose, flattened, shorter than the internodes; leaves 2.5-10 

 cm. long, about 2 mm. wide, smooth beneath, rough above: panicle usually- 

 contracted, the branches erect or ascending, 2.5 cm. long or less, spikelet- 

 bearing nearly to the base: spikelets 3-9-flowered, 3-6 mm. long: lower glumes 

 acute, 3-nerved; lemma 2-2.5 mm. long, obscurely 3-nerved, the nerves spar- 

 ingly pubescent toward the base. — Infrequent in our range; common eastward. 



3. Poa pratensis L. Sp. PI. 67. 1753. Cuhns 3-12 dm. high, sending out 

 numerous running rootstocks from the base: sheaths compressed, overlapping 

 below, ligule 1.5 mm. long; blades 1-6 mm. wide, those of the culm 5-15 cm. 

 long, the basal ones much longer: panicle pyramidal, the slender branches in 

 rather remote fascicles of 3-5, ascending, naked at base: spikelets crowded, 

 3-5-flowered, 4-5 mm. long: lemmas 3 mm. long, copiously webbed at base; 

 intermediate nerves strong, glabrous. Kentucky Blue Geass. June Grass. 

 (P. pseudopratensis Scrib. & Rydb. Contrib. Nat. Herb. 3: 532. 1896; P. phoe- 

 nicea Rydb. Bull. Torr. Bot. Club 32: 605. 1905.) — Europe, Asia, and America; 

 mostly as an introduced hay and pastiu'e grass, but incUgenous also in our 

 range. 



4. Poa flava L. Sp. PI. 68. 1753. Culms 4.5-15 dm. tall: leaves 5-15 cm. 

 long, 2-4 mm. wide, smooth or rough: panicle 1.5-3 dm. in length, open, the 

 branches spreading or ascending, 5-12 cm. long, divided and spikelet^bearing 

 above the middle: spikelets 3-5-flowered, 3-4 mm. long, exceeding their 

 pedicels, acute: lemma obtuse, somewhat webby at the base, 2-3 mm. long, 

 silky-pubescent on the lower half of the marginal nerves and the mid-nerve, 

 the intermediate nerves obscure or wanting. P. serotina. [P. crocaia Michx. 

 (?).]— Same ranges as the preceding; known as False Redtop and Fowl 

 Meadow Grass. 



5. Poa interior Rydb. Bull. Jorr. Bot. Club 32: 604. 1905. Culms 1.5-6 

 dm. tall, erect, slender, sometimes rigid: leaves 2.5-10 cm. long, 2 mm. wide 

 or less, erect, smooth or rough: panicle 5-12.5 cm. in length, open, the branches 

 erect or ascending, rarely spreading, 2.5-5 cm. long: spikelets 2-5-flowered, 

 3-5 mm. long: glumes acute or acuminate, 1-3-nerved; lemma obtuse or 

 acute, 2-2.5 mm. long, faintly 5-nerved, somewhat webby at base, the mid- 

 nerve and the marginal nerves silky-pubescent on the lower half. P. caesia 

 strictior. (P. memoralis of Am. authors as to the western plants; not P. 

 nemoralis L. P. glauca Vahl. also is here included.) — ^Very common; Rocky 

 Mountains to the Atlantic States. 



6. Poa platyphylla Nash. & Rydb. Bull. Torr. Bot. Club 28: 266. 1901. 

 Culms 5-8 dm. high, with slender roots: leaves flat; culm leaves 5-6, rather 

 broad and flat; the lower short; the upper 12-15 cm. long, sheathing the base 

 of the panicle; sheaths flattened, scabrous: panicle large and loose; its branches 

 distant, the lower mostly in threes, or rarely in fives and 10-12 cm. long, 

 capillary, erect at first but soon spreading: spikelets closely racemed on the 

 slender branchlets, mostly 3-flowered, 4-5 mm. long: glumes acute, unequal, 

 3-nerved, scabrous on the keel; lemma 5-nerved, sUghtly pubescent below and 

 on the keel and slightly webbed on the base. (P. ocddentalis Vasey, Contrib. 

 U. S. Nat. Herb. 1: 274. 1893, the earlier but untenable name. Lately fre- 

 quently distributed as P. leptocoma.) — Montana to Utah and New Mexico. 



7. Poa arcticaR. Br. in Parry's 1st Voyage, Supp. 288. 1824. Smooth and 

 glabrous: culms 1-4 dm. tall, erect, slender: leaves 2.5-10 cm. long, 1-2 mm. 

 wide: panicle 2.5-10 cm. in length, open, the branches generally widely spread- 

 ing and more or less flexuous, 2.5-6 cm. long: spikelets 3-5-flowered, 5-7 mm. 

 long: glumes acute or acuminate, 1-3-nerved; lemma about 4 mm. long, 

 faintly 5-nerved, the nerves short-pilose on the lower half, minutely pubescent 

 between the nerves, somewhat webbed at the base. — In the mountains of 

 Colorado and far northward. 



