270 GRASSES OF IOWA. 



obscurely toothed) at the blunt or rarely acute summit, glabrous, prom- 

 inently five to seven-nerved, the nerves parallel and separate. Squamu- 

 lae fleshy and truncate, or none. Stamens commonly 2. Styles present; 

 stigmas compoundly plumose. Ovary smooth. Grain oblong, free, the 

 furrow very narrow or none. Perennial, smooth, marsh grasses, mostly 

 with creeping bases or root-stocks; spikelets panicled. (Name from the 

 Greek word for sweet, in allusion to the taste of the grain.) 



Bentham & Hooker give the number of species as 30; reduced, how- 

 ever, by Hackel to 16; several of the included species in Bentham & 

 Hooker are excluded because of their lack of affinity with Glyceria. The 

 Section Atropis of Bentham & Hooker is excluded by Hackel and the 

 genus Puccinellia is placed under Atropis. Beal recognizes ten species 

 of Glyceria for North America. 



KEY TO THE SPECIES OF GLYCERIA. 



Spikelets ovate or oblong; panicle open. 



Spikelets 2-3 mm. long, branches of the panicle often drooping. 



— G. nervata. 1 ". 

 Spikelets 4-6 mm. long, branches of the panicle erect or ascending. 



— G. Americana.-. 

 Spikelets linear, 12 mm. long or more, panicle long and narrow. 



Flowering glume thick, hispidulous all over, truncate at the apex. 



— G. fluilans. 3 . 



Flowering glume thin, hispidulous on the nerves only, rounded at the 



apex G . borealis . 4 . 



1. GLYCERIA NERVATA. 



Glyceria nervata Trin. Mem. Acad. St. Petersb. VI. 1:365. 1831. 

 Watson and Coulter. Gray. Man. Bot. 667. pi. 10. 1890. (6 ed.) Scribner. 

 Grasses of Tenn. Bull. Univ. Tenn. Agrl. Exp. Sta. 7: 112. /. 153. 1894. 



Panicularia nervata Kuntze. Rev. Gen. PI. 2: 783. 1891. 



Panicularia nervata (Willd.) Kuntze. Beal. Grasses of N. A. 2: 

 567. 1896. Nash in Britton and Brown. 111. PI. 1:212. f.4SS. 1896. 

 Scribner. Bull. U. S. Dept. Agrl. Div. Agros. 7: 287. f. 2S1. 1900. (3 ed.) 



Poa nervata Willd. Sp. PI. 1: 389. 1798. 



DESCRIPTION. 



Nerved Manna Grass. A leafy perennial, 1 to 3 feet (2-6 dm.) 

 high, with an expanded, nodding panicle. Sheaths scabrous, ligule 1 to 

 2 lines (2-4 mm.) long, broadly truncate; leaf-blade 2 to 5 lines (4-10 

 mm.) wide, 6 to 12 inches (12-24 cm.) long, more or less scabrous 

 above, abruptly acute. Panicle 3 to 12 inches (6-24 cm.) long, usually 4 

 or 5 inches (8 or 10 cm.), pyramidal the spreading branches usually 



