106 



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



Annual blue- 

 Tufted, bright 



5. Poa annua L. 



GRASS. (Fig. 119.) 

 green, erect to spreading, sometimes 

 rooting at the lower nodes, usually 

 5 to 20 cm. tall, sometimes taller, 

 forming mats; culms flattened; blades 

 soft, lax, mostly 1 to 3 mm. wide; 

 panicle pyramidal, open, 3 to 7 cm. 

 long; spikelets crowded, 3- to 6- 

 flowered, about 4 mm. long; first 

 glume 1.5 to 2, the second 2 to 2.5 

 mm. long; lemmas not webbed at 

 base, distinctly 5-nerved, more or 

 less pubescent on the lower half of 

 all the nerves, the long hairs on the 

 lower part of the keel sometimes 

 simulating a web; anthers 0.5 to 

 1 mm. long. O —Open ground, 

 lawns, pastures, waste places, and 

 openings in woods, Newfoundland 

 and Labrador to Alaska, south to 

 Florida and California ; tropical Amer- 

 ica at high altitudes ; introduced from 

 Europe. In warmer parts of the 

 United States the species thrives in 

 the winter; in intermediate latitudes 

 it is a troublesome weed in lawns, 

 growing luxuriantly in spring, djang 

 in early summer and leaving un- 

 sightly patches. Occasionally found 

 in flooded places and stream banks, 

 the culms spreading. 

 2. Pratenses. — Perennials with slen- 

 der creeping rhizomes. Several 

 species dioecious. 



\ 



Figure 119. — Poa annua. Panicle, X 1; floret, X 10. 

 (Hitchcock, D. C.) 



\W 



Figure 120. — Poa compressa. Panicle, X 1; floret, 

 X 10. (Gayle 750, Maine.) 



6. Poa compressa L. Canada blue- 

 grass. (Fig. 120.) Culms solitary or 

 few together, often gregarious, strong- 

 ly flattened, wiry, decumbent at 

 base, bluish green, 15 to 70 cm. tall; 

 blades mostly rather short, 1 to 4 

 mm. wide; panicle narrow, 3 to 10 

 cm. long, the usually short branches 

 in pairs, spikelet-bearing to the base; 

 spikelets crowded, subsessile, 3- to 

 6-flowered, 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 ob- 

 scure. % — Open ground, open 

 woods, meadows, and waste places, 

 Newfoundland to Alaska, south to 

 Georgia, Tennessee, Alabama, Okla- 

 homa, New Mexico, and California; 

 introduced from Europe. Cultivated 

 for pastures in poor soil. 



7. Poa arachnifera Torr. Texas 

 bltjegrass. (Fig. 121.) Plants dioe- 

 cious; culms tufted, 30 to 75 cm. tall; 

 blades mostly 2 to 4 mm. wide, 

 scabrous above ; panicle narrow, com- 

 pact, more or less lobed or interrup- 



