Eleocharis tenuis (Willd.) Schult.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Perennial from a short stout rhizome; stems 2–6 dm, compressed or subterete; sheaths truncate and mucronate; spikelet cylindric, 6–16 mm; scales closely imbricate in many rows, broadly rounded above; bristles none; style trifid; achene yellow or yellowish-olive, 0.8–1 mm, obovoid, trigonous, its angles narrowly winged; tubercle minute, depressed-pyramidal to nearly flat. Pine-barren ponds; se. Mass. to Fla.; Mich.