Description

Key Characters:

Growth Form: Small annuals.

Stems: Culms tufted, 3–12 cm tall, 0.3–0.5 mm in diameter.

Roots: Fibrous root system.

Leaves: Leaves simple. Blades linear–filiform, much shorter than the culm, 0.4–1 mm wide. Apex gradually acuminate. Surfaces glabrate to sparsely pilose. Margins entire. Sheathing; sheaths pale to yellowish brown, 5–15 mm long, usually pubescent; ligule absent. Stipules absent.

Flowers: Flowers in inflorescences compound, lax, 2–4 cm long and wide, rays 3–7, filiform, 0.5–2.7 cm long, each one terminated by a single spikelet; involucral bracts 2–3, shorter than inflorescence, pilose or glabrate; spikelets 8–15–flowered, ovoid to narrowly ovoid, 2.5–5 mm long, 1–1.5 mm wide, subacute; glumes yellowish brown, membranous, ovate, 1–1.2 mm long, the keel green, apex mucronulate. Flowers bisexual (perfect). Corolla (petals) absent. Stamen 1. Ovary superior; styles filiform, glabrous at base, occasionally ciliolate below stigmas; stigmas 2.

Fruit: Achenes yellow; obovoid; biconvex; 0.6–0.7 mm long; faintly cancellate; apex rounded; base short–stipitate. Seeds 1; seed coat thin; free from pericarp; embryo basal; endosperm abundant.

Ploidy: 2n = 10

Habitat: Naturalized in ponds and taro fields.

Elevation Range: ca. 3 m.