GRAMINEAE. 143 



Spikelets ovate or oblong-, 8 mm. long or less. 



Flowering scales very broad, obscurely or at least not sharply nerved. 

 Panicle open, the branches ascending or spreading, often drooping. 

 Spikelets 3-5-flowered ; lowest flowering scale about 2 mm. long. 



1. P. I ax a. 

 Spikelets 5-12-flowered ; lowest flowering scale about 3 mm. long. 



2. P. Canadensis. 

 Panicle contracted, the branches erect. 3. P. obtusa. 



Flowering scales narrow, sharply and distinctly 7-nerved. 



Panicle elongated, its branches erect or appressed. 4. P. Torreyana. 



Panicle not elongated, open, its branches spreading or drooping, rarely erect. 

 Scales about 2 mm. long, obtuse or rounded at the apex. 



Spikelets 3 mm. long or less ; branches of the panicle often drooping. 



5. P. nervata. 

 Spikelets 4-6 mm. long ; branches of the panicle ascending or spreading. 



6. P. Americana. 

 Scales 2.5-3 rnm. r long, truncate and"denticulate at the apex. 



7. P. pallida. 

 Spikelets linear, 12 mm. long or more. 



Flowering scales 4-5 mm. long, obtuse, equalling or exceeding the obtuse palet. 

 Flowering scales firm, hispidulous all over, truncate at the apex. 



8. P. fluitans. 

 Flowering scales thin, hispidulous on the nerves only, obtuse at the apex. 



9. P. borealis. 

 Flowering scales 6-8 mm. long, shorter than the acuminate palet. 



Flowering scales obtuse, about 6 mm. long, a little exceeded by the palet. 



10. P. brachyphylla. 

 Flowering scales acute, about 8 mm. long, much exceeded by the palet. 



11. P. acntiflora. 



1. Panicularia laxa Scribn. Northern Manna-grass. (I. F. f. 484.) 

 Culms 6-12 dm. tall, smooth or slightly scabrous. Sheaths overlapping, rough; 

 leaves 2-4 dm. long, 4-8 mm. wide, very rough; panicle 17.5-22.5 cm. in length, the 

 branches spreading or ascending, the lower 7.5— 15 cm. long; spikelets 3-5 -flow- 

 ered, about 4 mm. long; empty scales unequal, scarious, acute. I -nerved, the first 

 one-half to two-thirds the length of the second; flowering scales broad, about 2 mm. 

 long, twice the length of the second scale, obtuse, obscurely 7-nerved. In water or 



vet soil. Me. to Penn. Aug. 



2. Panicularia Canadensis (Michx.) Kuntze. Rattlesnake-grass. (I. F. f. 

 485.) Culms 6-9 dm. tall, smooth or slightly scabrous. Sheaths shorter than the 

 internodes, those at the base of the culm overlapping; leaves 1.5-3 dm. long or 

 more, 4-8 mm. wide, rough; panicle 1.25-2.5 dm. in length, the branches spread- 

 ing, ascending or often drooping, 6. 25-12. 5 cm. long; spikelets 5-12-flowered. 5-8 

 mm. long, flattened, turgid; empty scales unequal, acute, I -nerved; flowering 

 scales broad, 3-4 mm. long, obtuse or acutish, obscurely 7-nerved. In swamps 

 and marshes, Newf. and N. B. to Ont. and Minn., south to N. J., Ohio and Kans. 

 The handsomest species of the genus. Ascends to 1500 m. in the Adirondacks. 

 July-Aug. 



3. Panicularia obtusa (Muhl.) Kuntze. Blunt Manna-grass. (I. F. f. 

 486. ) Culms 3-9 dm. tall, erect. Sheaths sometimes rough, strongly striate, the 

 lower overlapping; leaves 1.5-4 dm. long, 4-8 mm. wide, usually stiff, erect or 

 ascending, smooth beneath, more or less scabrous above; panicle 7.5-20 cm. in 

 length, contracted, dense, the branches erect; spikelets 3-7-flowered, 4-6 mm. 

 long; empty scales acute, scarious, I -nerved; flowering scales about 3 mm. long, 

 broad, obtuse, obscurely 7-nerved. In swamps, N. B. to N. Y. and central Penn., 

 south to Del. and Md. Ascends to 690 m. in the Catskill Mts. July-Aug. 



4. Panicularia Torreyana (Spreng.)Merr. Long Manna-grass. (I. F. f. 

 487.) Culms 6-9 dm. tall. Leaves lax, I.5-3 dm. long, 3-6 mm. wide, long- 

 acuminate, smooth beneath, rough above; panicle elongated, contracted, narrow, 

 usually nodding at the summit, 1. 5-3 dm. in length, the branches erect or appressed, 

 2.5-6 cm. long; spikelets 3-4-flowered, 3-4 mm. long; empty scales unequal, acute, 

 I -nerved; flowering scales narrow, about 2 mm. long, obtuse or acutish, distinctly 

 7-nerved. In wet woods, Newf. to Quebec and Minn., south to N. Car. and Ky, 

 Ascends to 1200 m. in the Adirondacks. Aug. -Sept. [P. efangata Kuntze.) 



