Genus 3. 



SEDGE FAMILY. 



Culms filiform ; scales obtuse. 22. B. tenuis. 



Culms flat; scales acute. 23. E. acuminata. 

 Tubercle subulate or narrowly pyramidal. 



Culms filiform, wiry, densely tufted, 4/-10' long. 24. E. intermedia. 



Culms flattened, slender, i°-a° long. 25. E.rostellata. 



1. Eleocharis interstincta (Vahl) R. & S. 

 Knotted Spike-rush. Fig. 758. 



Scirpus interstinctus Vahl, Enum. 2: 251. 1806. 

 Scirpus equisetoides Ell. Bot. S. C. & Ga. 1 : 79. 181 6. 

 Eleocharis interstincta R. & S. Syst. 2: 148. 1817. 

 Eleocharis equisetoides Torr. Am. Lye. 3: 296. 1836. 



Perennial by stout rootstocks, sometimes tuber- 

 iferous; culms terete, hollow, nodose, papillose, ii°-3° 

 tall, the sterile ones sharp-pointed. Sheaths oblique, 

 membranous, brown or green, the lower sometimes 

 bearing short blades ; spikelet terete, cylindric, many- 

 flowered, subacute, i'-ii' long, 2" in diameter, not 

 thicker than the culm ; scales ovate, orbicular or obo- 

 vate, 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, obtusely trigonous, 2 or 3 times as 

 long as the conic acute black tubercle. 



In water, Massachusetts to Wisconsin, Florida, the West 

 Indies and Mexico. July-Sept. 



2. Eleocharis mutata (L.) R. & S. Angled Spike-rush. Fig. 759. 



Scirpus mutatus L. Am. Acad. 5 : 391. 1760. 

 Scirpus quadrangulatus Michx. Fl. Bor. Am. 1 : 30. 1803. 

 Eleocharis quadrangulata R. & S. Syst. 2: 155. 1817. 

 Eleocharis mutata R. & S. Syst. 2 : 155. 1817. 



Perennial by stout rootstocks, sometimes tuberif- 

 erous; culms sharply 3-4-angled, stout, not nodose, 

 papillose, 2°-4° tall. Sheaths purplish-brown or green, 

 membranous, sometimes bearing short blades; spikelet 

 terete, acute, cylindric, i'-2' long, 2" in diameter, 

 many-flowered, about as thick as the culm; scales coria- 

 ceous, broadly ovate or obovate, obtuse or the upper 

 subacute, scarious-margined and sometimes with a nar- 

 row brown band within the margins, 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. 



In ponds, streams and swamps, Massachusetts to New 

 Jersey, Ontario, Michigan, Alabama, Missouri, Texas and 

 Guatemala. West Indies and South America. July-Sept. 



3. Eleocharis Robbinsii Oakes. 

 Fig. 760. 



Robbins' Spike-rush. 



Eleocharis Robbinsii Oakes, Hovey's Mag. 7: 178. 1841. 



'Perennial by slender rootstocks, culms slender, 3-angled, 

 continuous, 6'-2° long, sometimes producing numerous fili- 

 form flaccid 'sterile branches from the base. Sheaths ap- 

 pressed, obliquely truncate; spikelet subulate, few-flowered, 

 not thicker than the culm, 6"-io" long, .1" in diameter ; scales 

 lanceolate or oblong-lanceolate, obtuse or subacute, 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 very obtusely angled on the 

 back, somewhat longer than the conic-subulate flattened tu- 

 bercle, which has a raised ring around its base. 



In shallow water, Nova Scotia to Michigan, south to Florida. 

 Aug.-Sept. 



