Sitzungsber. Ges. Naturf., Freunde Berlin. 1868:17. 1868.
Stems profusely branched proximally to distally, 9–45 cm × 0.3–1 mm; internodes 0.3–5.2 cm, without prickes abaxially. Leaves ascending with age, 0.5–2.6 cm, stiff in age; sheath 0.7–2.8 mm wide, apex rounded; blade 0.2–1.3 mm wide, margins conspicuously serrulate, teeth 8–22 per side, apex acute, with 1 tooth, teeth multicellular; midvein without prickles abaxially. Flowers 1–2 per axil, staminate and pistillate on same plant. Staminate flowers in distal axils, 1.2–1.9 mm; involucral beaks 2-lobed, 0.3–0.5 mm; anther 4-loculed,1 mm. Pistillate flowers in proximal axils, 2 mm; styles to 0.7 mm; stigmas 4-lobed. Seeds not recurved, whitish, fusiform, 0.7–1.5 × 0.3–0.5 mm, apex with style situated at center; testa dull, 3 cell layers thick, pitted; aeroleareoles regularly arranged in 20 longitudinal rows, not ladderlike, 4–5-angled, longer than broad, end walls raised. Chromosome number unknown not available.
Phenology: Flowering late spring–fall.
Habitat: Slow moving streams and ponds
Elevation: 0–100 m
Introduced; Fla., Mexico, Central America (Guatemala, Belize, Honduras), West Indies (Cuba).