Herbs, perennial, rhizomatous to cespitose, 0.5--4 dm. Rhizomes 1--2 mm diam., not swollen. Culms erect, terete, 1--3 mm diam., smooth. Cataphylls 0--1, straw-colored to chestnut brown, apex acute. Leaves: basal 1--2, cauline 0--1; auricles 1--1.2 mm, apex rounded to acute, membranaceous or scarious; blade green to straw-colored, terete, 3--15 cm x 0.3--0.6 mm. Inflorescences terminal single head (rarely cluster of 2 heads), 0.5--1.6 cm; primary bract erect; heads 12--60-flowered, spheric (to hemispheric), 4.5--15 mm diam. Flowers: tepals dark purplish brown to black, lanceolate to lance-ovate, apex acute, mucro subulate; outer tepals 2.4--4.9 mm; inner tepals 2.3--4.3 mm; stamens 6, anthers 1/4 to equal filament length. Capsules included or slightly exserted, chestnut brown, 1-locular, obovoid, 1.9--3.5 mm, apex obtuse or rounded, valves separating at dehiscence, fertile throughout or only proximal to middle. Seeds ellipsoid, 0.4--0.5 mm, not tailed; body clear yellow-brown. 2n = 40.
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