184 CYPERACEAE 



perianth -bristles overtopping the body of the achene : achenes broadly obovoid, fully 1 mm. 

 long ; tubercle about as high as the body of the achene. 

 In moist soil, Arkansas to Texas. Summer and fall. 



17. Eleocharis nodulosa (Roth) Schult. Perennial by horizontal rootstocks. Scapes 

 closely tufted, relatively stout, 3-10 dm. tall, copiously nodose-septate, invested at the base 

 by more or less discolored sheaths, constricted below the summit : spikelet conic-cylindric, 

 acute, 1-2 cm. long, 4-6 mm. thick : scales closely imbricated, oblong-lanceolate, often con- 

 stricted below the apex, 3-4 mm. long, scarious-margined : perianth-bristles very variable 

 in length : achenes obovoid, pinched at the base, about 1 mm. long, plump ; tubercle 

 deltoid, about the width of the body of the achene. 



In swamps, Florida to Louisiana and Arizona. Also in tropical America. Spring to fall. 



18. Eleocharis macrcstachya Britton. Perennial by relatively short rootstocks, 

 pale green or straw-colored. Scapes tufted, 2.5-12 dm. long, stout: spikelet narrowly 

 cylindric or linear-lanceolate in outline, 1-2.5 cm. long, many-flowered, acute: scales ob- 

 long-ovate to lanceolate, often rather acute, pale green or straw-colored with darker ribs : 

 perianth-bristles 5-6, as long as the achene or somewhat shorter, retrorsely barbed, or 

 sometimes very short: stigmas 2: achenes lenticular, obovoid, about 1.5 mm. long, ex- 

 cluding the small cap-like tubercle, lemon-yellow. 



In low grounds, Arkansas to Nevada, Louisiana, Texas and Arizona. Spring to fall. 



19. Eleocharis glauc6scens (Willd. ) Schult. Perennial by horizontal rootstocks. 

 Scapes tufted, slender, 1-9 dm. long, bright or deep green : spikelet oblong or oblong-lan- 

 ceolate, 0.5-1.5 cm. long, acute or rather obtuse : scales brown or dark green, blunt or 

 acute in age : perianth-bristles usually 4, about as long as the achene or shorter or nearly 

 wanting: stigmas 2 : achenes lenticular, obovoid, about 1.5 mm. long, excluding the nar- 

 row conic tubercle, brown. 



In swamps or meadows, Ontario to Minnesota, Nebraska, Florida and Texas. Spring to fall. 



20. Eleocharis Ravenelii Britton. Perennial, bright green. Scapes tufted, 3-5 

 dm. long, slender: spikelet lanceolate or oblong-lanceolate in outline, 8-11 mm. long, 

 acute : scales oblong to oblong-lanceolate, rather blunt, scarious-margined, brown on either 

 side of the prominent midrib : perianth-bristles 4-5, somewhat shorter than the achene : 

 stigmas 2 : achenes biconvex, plump, 1 mm. long or less, narrowly obovoid, somewhat con- 

 stricted at the top, smooth or nearly so ; tubercle depressed. 



In sandy soil, southern Texas. Spring. 



21. Eleocharis aciculaiis (L. ) K. & S. Perennial by filiform stolons or rootstocks. 

 Scapes tufted, finely filiform or setaceous, obscurely 4-angled and grooved, weak, erect or 

 reclining, 5-20 cm. long : sheaths truncate : spikelet compressed, narrowly ovate or linear- 

 oblong, acute, broader than the scape, 3-10-flowered, 3-10 mm. long, 1 mm. wide : scales 

 oblong, obtuse, or the upper subacute, thin, pale green, usually with a narrow brown band 

 on each side of the midvein, deciduous, many of them commonly sterile : perianth-bristles 

 3-4, fragile, fugacious, shorter than the achene: stigmas 3: achenes obovoid-oblong, 0.5 

 mm. long, pale, obscurely 3-angled with a rib on each angle and 6-9 lower intermediate 

 ribs connected by fine ridges ; tubercle conic, acute, ^ as long as the achene. 



In wet soil, throughout North America, except the extreme north. Also in Europe and Asia. 

 Summer and fall. A variety, E. acicularis radicans (Poir.) Britton, is distinguished by its relatively 

 stout scapes and thicker spikelets. Texas, California and Central America. 



22. Eleochaiis Chaetaria R. & S. Perennial or annual. Scapes tufted, 2-20 cm. 

 long, curved, filiform or wire-like, smooth, barely constricted at the summit, with a green 

 sheath at the base : spikelet erect, oblong or ovoid-oblong, 2-3 mm. long, 1-4-flowered, 

 flattened : scales in 2 or 3 rows, thin, barely discolored : perianth-bristles 6, about as long 

 as the achene, sometimes much reduced : stigmas 3 : achenes 3-angled, obovoid, barely 1 

 mm. long ; tubercle pyramidal, shorter than the body of the achene. 



In sandy soil or low grounds, southern Alabama. Also in the West Indies and most tropical and 

 warm-temperate regions. Spring to fall. 



23. Eleocharis vivipara Kunth. Perennial by horizontal rootstocks, pale green. 

 Scapes very numerous, tufted, very slender, 1-3 dm. long, not rigid, sometimes spreading, 

 barely constricted at the summit : spikelet linear-oblong, 4-7 mm. long, acutish, often 

 sparingly proliferous : scales oblong or ovate-oblong, blunt, scarious-margined, closely im- 

 bricated, somewhat discolored : perianth-bristles 6, barbed, unequal in length : achenes ob- 

 ovoid, nearly white, 3-angled, plump, about 1 mm. long, finely cancellate ; tubercle deltoid, 

 or depressed, shorter than the body of the achene. 



In low grounds and on shores, South Carolina to Florida and Texas. Summer and fall. 



2. Eleocharis tdrtilia ( Link ) Schult. Annual. Scapes tufted, filiform, sharply 3- 

 angled, pale green, erect or reclining, twisting when old, 3-4 dm. long : sheaths obliquely 

 truncate, 1-toothed : spikelet ovoid or oblong, rather acute, several-flowered, 4-6 mm. long, 

 about 2 mm. thick, much thicker than the scape : scales firm, pale, ovate, mostly obtuse : 



