19. Section Paludosae G. Don

Plants monoecious, the rhizomes well developed and long-creeping, forming large clumps or colonies, the aerial stems well spaced. Vegetative stems present, actually false stems composed nearly entirely of a series of overlapping leaf sheaths. Flowering stems erect to ascending, sharply trigonous, glabrous, shorter than to longer than the leaves, brown or reddish purple at the base. Leaves basal and on the basal half of the stems, glabrous. Leaf sheaths with the tip deeply concave, the lowermost sheaths brown or reddish to purplish tinged, the ligule variously shaped. Spikes 3–8 per stem, the uppermost 1–4 staminate, the lowermost 2–4 pistillate, the bracts leaflike, lacking sheaths or the lowermost with short sheaths. Terminal, staminate spike stalked, the lateral staminate spikes (if present) sessile or nearly so, closely spaced to somewhat separated along the axis, erect to ascending, linear to narrowly oblong in outline. Pistillate spikes loosely spaced along the axis, none basal, sessile or short-stalked, ascending, cylindrical, with numerous, ascending to somewhat spreading, densely overlapping perigynia, the uppermost occasionally with a few staminate flowers. Perigynia thick-walled, circular in cross-section or nearly so, tapered to a short, straight, somewhat flattened beak ending in 2 short, stiff teeth 0.3–1.0 mm long, rounded at the base, more or less sessile, the surface variously nerved, glabrous or hairy. Styles withering during fruit development, jointed to the main body of the short-beaked fruit, or persistent, forming a hard, bony beak similar in texture to the main body of the fruit. Stigmas 3. Fruits elliptic-obovate in outline, trigonous with flat to somewhat concave sides and blunt angles, yellowish brown to greenish brown. About 25 species, U.S., Canada, South America, Europe, Asia, Africa, Pacific Islands.