Scirpus retroflexus Poiret in J. Lamarck et al., Encycl. 6: 753. 1804; Baeothryon retroflexum A. Dietrich; Chaetocyperus niveus Liebmann; C. polymorphus Lindley & Nees var. depauperatus Nees; C. rugulosus Nees; C. viviparus Liebmann; Cyperus depauperatus Vahl; Eleocharis depauperata Kunth

Plants annual, tufted, mat-forming, often stoloniferous, sometimes entirely vegetative; rhizomes absent. Culms erect, ascending or arching, pentagonal, sulcate, 1.5–10 cm × 0.2–0.3 mm [larger], soft. Leaves: distal leaf sheaths persistent or disintegrating, pale brown to green, red-spotted [mostly red-brown], membranous; apex acuminate. Spikelets: basal spikelets usually present, bisexual; often proliferous, ellipsoid or obovoid, laterally compressed, 1.7–3.9 × 1.2–2 mm, apex acute; proximal scale empty or with a flower, deciduous, amplexicaulous, similar to floral scales (sometimes 2.4–2.9 mm); subproximal scale with a flower; floral scales clearly distichous, 2–6 [or more], 4–6 per mm of rachilla, pale brown [marked red-brown], ovate or elliptic, 1.8–2.5 × 0.8–1.4 mm, membranous, apex rounded to obtuse, midribs green, keeled. Flowers: perianth bristles 6, colorless or pale brown, shorter than achenes; spinules not evident at 45X; stamens 3; anthers (0.55–)0.7 mm; styles 3-fid. Achenes stramineous (to cream), obovoid, trigonous or subterete, not compressed, angles prominent, 0.8 × 0.5–0.55 mm, apex not constricted proximal to tubercle, coarsely cancellate or honeycomb-reticulate at 10–15X. Tubercles red-brown, pyramidal, trigonous, proximally clearly to obscurely 3-lobed, lobes decurrent on achene angles, 0.3–0.35 × 0.3–0.4 mm.

Fruiting summer. Freshwater ponds, stream banks, marshes, sandy or muddy soils; 0–10 m; Ala.; Mexico; West Indies; Bermuda; Central America; South America; Asia (including Indonesia); Pacific Islands; Australia.

We have seen only one collection of Eleocharis retroflexa from the flora area (Mobile, Alabama, in 1896, US). Other populations are likely in the United States Gulf States. The broad-shouldered, strongly sculptured achenes, trilobed, decurrent tubercles, and basal spikelets are distinctive.