Leaves: stipules connate; blade 1.4--6.5 cm ´ 0.5--1.9 mm, apex acute or rarely apiculate, rarely with bristle, lacunae present or absent, 0--2 rows each side of midrib; veins 1--3. Inflorescences: peduncles 1--3 per plant, filiform to cylindric; spikes cylindric, interrupted. Fruits obovoid, sides centrally concave; beak toward adaxial edge, rarely median. 2n = 26 (Eurasia).
Leaves 1-3-veined, 1.4-6.5 cm x 0.5-1.9 mm, the apex acute or rarely apiculate, rarely with a bristle, lacunae absent or to 2 rows each side of midrib; ligules usually connate. Peduncles filiform to cylindrical, 1-3 per plant; spikes cylindric, usually interrupted. Fruits obovate, the sides usually centrally depressed; beak forward, rarely central.
Nearly cosmopolitan. In the Neotropics, it is fairly common from Mexico south to Argentina and Chile at elevations from sea level to 2500 m, although it is not known in the Guayana area. The taxon occurs in lakes, ponds, streams, and marshes, especially those that are slightly calcareous.