1 68 FLORA. 



Achene smooth. 



Tubercle flat, covering the top of the black achene. 



1 6. E. melanocarpa. 

 Tubercle ovoid-conic, acute, contracted at the base. 



17. E. albida. 

 Achene papillose. 



Achene 3-ribbed on the angles. 18. E. tricostata. 



Achene obtuse-angled, not ribbed. 



Culm filiform ; scales obtuse. 19. E. tenuis. 



Culm flat ; scales acute. 20. E. acuminata. 



Tubercle subulate or narrowly pyramidal. 



Culms filiform, wiry, densely tufted, 1-2.5 dm. long. 



21, E. intermedia. 

 Culms flattened, slender, 3-6 dm. long. 22. E. rostellata. 



1. Eleocharis interstincta (Vahl) R. & S. Knotted Spike-rush. (I. F. f. 

 577.) Perennial by stout rootstocks; culms terete, hollow, nodose, papillose, 

 0.4-0.9 m. tall, the sterile ones sharp-pointed. Sheaths membranous, the lower 

 sometimes bearing short blades; spikelet terete, cylindric, many-flowered, sub- 

 acute, 2.5-4 cm. long, 4 mm. in diameter, not thicker than the culm; scales ovate, 

 orbicular or obovate, obtuse or the upper acute, narrowly scarious-margined, 

 faintly many-nerved, persistent; bristles about 6, rigid, retrorsely barbed, as long 

 as the body of the achene or shorter; stamens 3; style 3 -cleft, exserted; achene 

 obovoid, brown, shining, with minute transverse ridges, convex on one side, very 

 obtusely angled on the other, 2 or 3 times as long as the conic acute black broad- 

 based tubercle. In water, Mass. to Mich., the W. I. and Mex. July-Sept. 



2. Eleocharis mutata (L.) R. & S. Quadrangular Spike-rush. (I. F. f. 

 578.) Perennial by stout rootstocks; culms sharply 4-angled, stout, not nodose, 

 papillose, 0.6-1.2 m. tall. Sheaths purplish-brown or green, sometimes bearing 

 short blades; spikelet terete, cylindric, 2-5 cm. long, 4 mm. in diameter, many- 

 flowered. about as thick as the culm; scales coriaceous, broadly ovate or obovate, 

 obtuse or the upper subacute, scarious-margined, faintly many-nerved, persistent; 

 bristles about 6, rigid, retrorsely barbed, about as long as the achene ; stamens 3 ; 

 style 3 -cleft; achene obovoid, biconvex or slightly angled on the back, minutely 

 cancellate, about twice as long as the conic acute tubercle, which is truncate or con- 

 tracted at the base. In ponds, streams and swamps, N. N. J. to S. Ont. Mich, south 

 to Ala., Mo., Tex. and Guatemala. Also in the W. I. and S. Am. July-Sept. 



3. Eleocharis Robbinsii Oakes. Robbins' Spike-rush. (I. F. f. 579.) 

 Perennial by slender rootstocks; culms slender, 3-angled, 0.1-5 m> l° n g> some- 

 times producing numerous filiform flaccid sterile branches from the base. Sheaths 

 appressed, obliquely -truncate; spikelet subulate, few-flowered, not thicker than 

 the culm, 1-2 cm. long, 2 mm. in diameter; scales lanceolate or oblong- lanceolate, 

 strongly concave, faintly several-nerved, persistently clasping the rachis, narrowly 

 scarious-margined; style 3-cleft; bristles 6, equalling the achene and tubercle, 

 retrorsely barbed; achene obovoid, light brown, biconvex or obtusely angled on 

 the back, longer than the conic-subulate flattened tubercle, which has a raised ring 

 around its base. In shallow water, N. B. to Mich., south to Fla. Aug-Sept. 



4. Eleocharis ochreata (Nees) Steud. Pale Spike-rush. (I. F. f. 580.) 

 Perennial by slender rootstocks; culms very slender, or filiform, pale green, 

 3-angled, 5-25 cm. tall. Upper sheath with a white, hyaline, scarious limb; 

 spikelet subacute, 2-3 times as thick as the culm, about 4 mm. long, 2-3 mm. in 

 diameter, several -flowered; scales pale green, oblong-lanceolate, obtuse or the 

 upper acute, thin, hyaline with a faint mid vein; style 2-cleft; bristles about 6, 

 slender, retrorsely barbed, somewhat longer than the achene; 0.5 mm. long, 

 lenticular, obovate, smooth, brown, 2-4 times as long as the conic acute tubercle, 

 which is often constricted at the base. In wet soil, S. Va. to Fla. and Miss. Also in 

 trop. Amer. Aug. -Sept. 



5. Eleocharis olivacea Torr. Bright green Spike-rush. (I. F. f. 581.) 

 Perennial by running rootstocks, often tufted and matted; culms very slender, bright 

 green, erect or reclining, flattened, 2-10 cm. long. Upper sheath with a white 

 hyaline limb; spikelet ovoid, much thicker than the culm, several-many-nowered„ 

 about 4 mm. long, 2 mm. in diameter; scales ovate, thin, acute, reddish brown. 

 with a green midvein and narrow, scarious margins; stamens 3; style 2-clefi; bris- 



