4(1). Lemmas with 5 prominent nerves; second glume 3-nerved; sheaths open 

 7. G. pauci flora. 



4. Lemmas with 7 usually prominent nerves; second glume 1 -nerved; sheaths (at 



least the upper) closed from below the summit (5) 



5(4). First glume more than 1 mm. long, usually about L5 mm. long 



6. G. grandis. 



5. First glume not more than 1 mm. long (6) 



6(5). Blades 2-4 mm. wide, sometimes to 8 mm., rather firm, often folded; first 

 glume 0.5 mm. long 4. G. striata. 



6. Blades 6-12 mm. wide, flat, thin, lax; first glume about 1 mm. long 



5. G. elata. 



1. Glyceria borealis (Nash) Batchelder. Northern manna-grass. Fig. 80. 

 Culms erect or decumbent and rooting at the base, slender, 3-10 dm. tall; 



sheaths smooth or slightly scabrous, keeled; blades flat or folded, usually 2-6 mm. 

 wide, very narrow; panicle mostly 2-4 dm. long, very narrow, the branches as 

 much as 1 dm. long, bearing several closely appressed spikelets; spikelets mostly 

 6- to 12-flowered, 1-1.5 cm. long; glumes oblong, scarious, the first glume 1.5-2 

 mm. long, the second 3-4 mm. long; lemmas rather thin, obtuse, 3-4 mm. long, 

 strongly 7-nerved, broadly scarious at the tip, minutely scabrous on the nerves, 

 otherwise glabrous. 



Shallow water in wet meadows or lake margins, in N. M. {Hitchcock) and 

 Ariz. (Coconino, Apache, Cochise and Pima cos.); Nfld. to Alas., s. to Pa., 111., 

 Minn, and Wash., in mts. to N. M., Ariz, and Calif. 



2. Glyceria arkansana Fern. 



Tufted perennial; culms stout, 10-15 dm. long, erect; panicles 35-50 cm. long, 

 with a number of ascending floriferous branches 0.4—1 mm. thick, rather rigidly 

 straight; spikelets 10- to 14-flowered, nearly sessile, appressed, remote; lemmas 

 2.5-3.5 mm. long, minutely pubescent. Probably only a form of G. septentrionalis. 



In marshy areas, roadside ditches, along sloughs and in swampy ground, in 

 Okla. (McCurtain Co.) and possibly Tex., spring-summer; also La. and Ark. 



3. Glyceria septentrionalis Hitchc. 



Like G. arkansana but lemmas merely minutely scabrous and 3.5-5 mm. long. 

 In shallow water and borders of sloughs and lakes and in marshy areas and road- 

 side ditches in e. and s.e. Tex., spring-summer; e. N.A. w. to Wise, la., Mo., 

 Ark. and Tex. 



4. Glyceria striata (Lam.) Hitchc. Fowl manna-grass. Fig. 81. 



Perennial forming mats by means of short rhizomes; panicles 1-2 dm. long, 

 with numerous slender ascending-diverging branches about 0.2 mm. thick (in 

 turn bearing even more slender floriferous branchlets); pedicels 0.5-1 mm. long, 

 appressed; spikelets 3- to 7-flowered, ovate in outline; lemmas 1.5-2.1 mm. long. 



Rare at the margins of clear permanent streams in limestone areas, in wet 

 meadows, bogs and shallow water of ponds and lakes, drainage ditches and 

 sloughs in Okla. (Johnston and Murray cos.) and in the Tex. Trans-Pecos 

 (Guadalupe Mts.) and e. part of Edwards Plateau, N.M. (Otero, Taos, San 

 Miguel and Sandoval cos.) and Ariz. (Coconino, Apache, Navajo and Gila cos.), 

 spring-summer; most of the temp, parts of N. A. 



5. Glyceria elata (Nash) Hitchc. 



Culms erect, smooth, succulent, dark green, 1-2 m. tall; sheaths scabrous; 

 blades flat, usually 6-9 mm. or sometimes only 4 mm. wide, scabrous; panicle 

 large and diffuse, becoming oblong, 15-30 cm. long, the branches naked below, 

 the lower ones usually reflexed at maturity; spikelets 3-5 mm. long, oblong or 



183 



