Cyperus pedunculatus (R. Brown) J. Kern

Rhizomes long, much branched, buried in sand. Culms to 12 cm × 2 mm, smooth. Leaves: sheath apices truncate; blades with keeled midrib, linear-lanceolate, 3–8 cm × 2–6 mm, leathery, margins scabridulous. Inflorescences: bracts 1–6, leaflike; spikes 1–6, densely ovoid. Spikelets ovoid to ellipsoid; rachilla deciduous, articulate at base, internodes 2–2.6 × 1 mm, corky, wings persistent, clasping (enclosing) achene; bract ovate, 2–2.5 mm; prophyll ovate-lanceolate, 1.5 mm; floral scales 2–3, off-white to reddish brown, 5–9-veined, ovate, 3.3–3.6(–4) × 1.3–1.7 mm. Flowers: stamen filaments 2–3.2 mm; anthers linear, 0.9–1.2(–1.6) mm; connective apices reddish, 0.1–0.4 mm, glabrous; styles 0.5–1 mm; stigmas 2 mm, glabrous. Achenes brown, substipitate, oblong to ellipsoid, 1.8–2 × 0.5–0.6 mm, apex acute, papillose.

Fruiting early summer. Sand dunes and upper edges of beaches; 0–10 m; Fla.; West Indies; South America; Asia; Africa; Pacific Islands; Australia.

It is easy to mistake the corky rachilla segment, which tightly clasps the mature achene, for a part of the achene (or for an achene). The rachilla segment is smooth, fawn brown, and biconvex in cross section; the achene is dark brown, papillose, and trigonous in cross section.