4. Kyllinga polyphylla Kunth, Enum. Pl. 2: 134. 1837.
水蜈蚣 shui wu gong
Cyperus aromaticus (Ridley) Mattfeld & Kükenthal; Kyllinga aromatica Ridley; K. erecta Schumacher var. polyphylla (Kunth) Hooper.
Perennials. Rhizomes thick, horizontally long creeping, internodes short, clothed with brown to purple or blackish scales, with 1 culm at each node. Culms scattered, 25-90 cm tall, 3-angled, smooth, base bulbous, clothed with long leaf sheaths. Leaf sheath purplish, cylindric, margin scarious, mouth obliquely truncate, apex subacute, apical 1 or 2 with a blade; leaf blade 3-5(-15) cm × 2-6 mm or shorter, flat, apical margin denticulate. Involucral bracts 5-8, leaflike, longest to 15 cm, ± horizontal to slightly reflexed. Spikes 1-3, hemispheric to subglobose, 6-12 × 6-8 mm; lateral spikes much smaller, with numerous densely arranged spikelets. Spikelets narrowly ellipsoid-ovoid, ca. 3 mm, 1- or 2-flowered. Glumes straw-colored with rusty brown striae, ovate-lanceolate, 3-4 mm, 5-7-veined, midvein ± spinulose, apex mucronate. Stamens 3; anthers shortly linear; connective prominent beyond anthers. Style long; stigmas 2, shorter than style. Nutlet yellowish white at first but black when mature, oblong to obovoid-oblong, ca. 1/2 as long as subtending glume, plano-convex, densely puncticulate, apex apiculate. Fl. and fr. Jul-Oct.
Naturalized in moist or brackish sandy areas; below 300 m. Hong Kong, Taiwan [native to tropical Africa, Indian Ocean islands, and Madagascar].
Kyllinga polyphylla is also naturalized in tropical America, Asia, Australia, and Pacific islands.