GRASSES OF IOWA. 253 



KEY TO THE SPECIES OF POA. 



Culms low and tufted, spreading, annual or biennial. 



Flowering glume 5-nerved, not webby at the base P. annua. '. 



Flowering glumes 3-nerved. or obscurely 5-nerved, webby at the base 



— P. Chapmaniana. "-. 

 Culms low, geniculate-ascending, from a creeping rootstock, much flattened; 



panicle simple and contracted P. compressa. 3 . 



Culms tall, terete, tufted, perennial. 



Flowering glumes 3 mm. or less long, web at base much shorter. 



Flowering glumes glabrous except for the web at base../ 1 , debilis. *. 



Flowering glumes pubescent on the midnerve only. .../'. trivialis. 5 



Flowering glumes pubescent on the midnerve and marginal nerves, 



at least on the lower half. 



Flowering glume silky villous, long web at base. . .P. Wot 'fit. r \ 



Intermediate nerves obscure or wanting. 



Culm usually 4 dm. or less tall, the panicle usually less 



than 1 5 dm. long P. nemoralis . " . 



Culm usually 6-10 dm. tall, panicle elongated, usually 2-4 



dm. long P. flava. 8 . 



Intermediate nerves prominent P. pratensis. '■'. 



Flowering glumes 4-5 mm. long, web at base long and copious, exceed- 

 ing the scale P. arachnifera. 10 . 



1. POA ANNUA. 



Poa annua L. Sp. PI. 68. 1753. Watson and Coulter. Gray. Man. 

 Bot. 664. 1890. (6 ed.) Scribner. Grasses of Tenn. Bull. Univ. Tenn. Agrl. 

 Exp. Sta. 7: 106. /. 141. 1894. Beal. Grasses of N. A. 2: 530. 1896. 

 Nash in Britton and Brown. 111. Fl. 1: 201. /. 459. 1SP6. Scribner. Bull. 

 U. S. Dept. Agrl. Div. Agros. 17: 237. /. 533. 1899. 



DESCRIPTION'. 



Low Spear Grass. Annual Meadow Grass. A low, spread- 

 ing annual, the erect or ascending, somewhat flattened stems 2 to i :. 

 inches (4-24 cm.) high. Sheaths smooth, lax; leaf-blade flat, smooth, 

 spreading, I to 1^ lines (2-3 mm.) wide, 1 to 3 inches (2-6 cm.) long. 

 Panicle short, pyramidal, the primary branches spreading, solitary or in 

 pairs. Spikelets ovate or oblong, three to six-flowered, about 2 lines 

 (4 mm.) long; empty glumes somewhat unequal, the first one-nerved, 

 the second three-nerved; flowering glumes about 1 line (2 mm.) long, 

 distinctly five-nerved, all the nerves more or less hairy below, the base 

 of the flowering glume pilose. Palea two-keeled, keels hairy. May to 

 September. 



Poa annua occurs only in cities. Especially in eastern Iowa. Found 

 along the river as far north as Clinton and Mason City. It has been 

 found in Iowa chiefly in shady lawns, and near buildings. 



