106 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



Figure 167.— Poa annua 

 Panicle, X 1; floret, X 10 

 (Hitchcock, D.C.) 



2. Pratenses. — Perennials with slender creeping rhizomes. Several 

 species dioecious. 



6. Poa compressa L. Canada bluegrass. (Fig. 168.) Culms 

 solitary or few together, often gregarious, strongly flattened, wiry, 

 decumbent at base, bluish green, 15 to 50 cm 

 tall ; blades rather short, mostly 1 to 4 mm wide ; 

 panicle narrow, 3 to 7 cm long, the usually 

 short branches in pairs, spikelet-bearing to the 

 base; spikelets crowded, subsessile, 3- to 6-flow- 

 ered, 4 to 6 mm long; glumes 2 to 3 mm long; 

 lemmas firm, 2 to 3 mm long, the web at base 

 scant or wanting, the keel and marginal nerves 

 slightly pubescent toward base, the intermediate 

 nerves obscure. % — Open ground, open woods, 

 meadows, and waste places, Newfoundland to 

 Alaska, south to Georgia, Tennessee, Alabama, 

 Oklahoma, New Mexico, and California; intro- 

 duced from Europe. Cultivated for pastures in 

 poor soil. 



7. Poa arachnifera Torr. Texas bluegrass. 

 (Fig. 169.) Plants dioecious; culms tufted, 30 

 to 50 cm tall; blades mostly 2 to 4 mm wide, 

 scabrous above; panicle narrow, 

 compact, more or less lobed or 

 interrupted, 5 to 12 cm long; spikelets mostly 5- to 

 10-flowered, the pistillate conspicuously cobwebby, the 

 lemmas 5 to 6 mm long, acuminate, copiously long 

 webby at base, the strongly compressed keel and lateral 

 nerves ciliate-f ringed along the lower half; staminate 

 lemmas glabrous or with a scant web at base. % 

 — Prairies and plains, southern Kansas to Texas and 

 Arkansas; introduced eastward to South Carolina and 

 Florida; Idaho (fig. 170). Sometimes cultivated for 

 winter pasture. 



8. Poa macrantha Vasey. (Fig. 171.) Plants dioe- 

 cious; culms erect from a decumbent base, with exten- 

 sively creeping rhizomes, and also long runners creep- 

 ing over the sand, 15 to 40 cm tall; sheaths tawny, 

 papery; blades involute, subflexuous; panicle contrac- 

 ted, sometimes dense and spikelike, 5 to 12 cm long, 

 pale or tawny; spikelets about 12 mm long, about 5- 

 flowered; glumes 3-nerved, or the second indistinctly 

 5-nerved, about 8 mm long; lemmas about 8 mm long, 

 short- webbed at base, pubescent on the keel and mar- 

 ginal nerves below, slightly scabrous on the keel above ; 

 pistillate florets with abortive stamens. % — Sand 

 dunes along the coast, Washington to northern 

 California. 



9. Poa douglasii Nees. (Fig. 172.) Plants dioecious, 

 the two kinds similar; culms ascending from a decumbent base, usually 

 less than 30 cm tall ; rhizomes slender; sheaths glabrous, tawny and pa- 

 pery; blades involute, some of them usually exceeding the culm; panicle 



Figure 168.— Poa 

 compressa. Pan- 

 icle, X 1; floret, X 

 10. (Gayle 750, 

 Maine.) 



