Rhizomes (1-)1.5-2 mm thick, hard, longer internodes 2 mm, scales decaying to fibers. Culms bluntly angled to smooth, seldom deeply sulcate, to 0.5 mm wide. Leaves: distal leaf sheaths without tooth, or rarely with slender apical tooth to 0.2 mm. Flowers: perianth bristles absent. Achenes dark brown, dark green, or yellow, coarsely (to finely) rugose at 10X, usually coarsely cancellate at 10-20X, 6-10 prominent depressions in each vertical series. Tubercles greatly depressed, rarely pyramidal. 2n = 20. Fruiting summer. Fresh, often calcareous, shores, wet woods, ditches; 10-600 m; Ala., Ark., D.C., Ga., Ill., Ind., Iowa, Kans., Ky., La., Md., Mo., Nebr., Okla., Pa., S.Dak., Tenn., Tex., Va., W.Va., Wis. Occasionally plants of Eleocharis tenuis var. verrucosa are found mostly submerged. Harms used a chromosome number as a basis for raising Eleocharis tenuis var. verrucosa to a species (L. J. Harms 1972), but he did not correlate chromosomes with morphology, and I have not located any of his voucher specimens. There are too few chromosome number reports for use in defining taxa in the E. tenuis complex (A. E. Schuyler 1977).