Plants perennial, cespitose, 40-100(-150) cm; rhizomes absent. Culms arching, leafy, obscurely and convexly trigonous, multi-ribbed, slender to stoutish. Principal leaves overtopped by culm; blades linear, flat proximally, 1.5-3 mm wide, apex tapering, trigonous. Inflorescences: spikelet clusters 3-several, widely spaced, often equidistant, mostly hemispheric to globose, occasionally lobed, 1-2 cm thick; bracteal leaves much exceeding subtended inflorescence. Spikelets dark red-brown to dark brown, lance ellipsoid to ellipsoid, 4-5(-6) mm, apex acute; fertile scales elliptic, 3-3.5(-4.5) mm, apex acute, midribs 3, laterals indistinct. Flowers: perianth bristles 6, reaching tubercle tip, retrorsely (rarely antrorsely) barbellate. Fruits 1(-2) per spikelet, 3.5-4(-4.2) mm; body brown with pale center, obovoid distal to stipe, lenticular, 2-2.3 × 1-1.5(-2) mm; tubercle triangular-subulate, (1-)1.5-2 mm, at least 0.5 mm wide at base.

Fruiting summer-fall. Sandy silts, sands, and peats of shores, boggy streams, seeps, savannas, and savanna bogs; 0-200 m; Ala., Del., Fla., Ga., La., Md., Miss., N.J., N.Y., N.C., S.C., Tex., Va.

North American plants referred to Rhynchospora axillaris (Lamarck) Britton [Phaeocephala axillare (Lamarck) House by N. L. Britton and A. Brown (1913) and J. K. Small (1933)] are actually R. cephalantha. A photograph of the type specimen of Schoenus axillaris Lamarck (from P) reveals what appears to be an immature top of S. glomeratus [R. glomerata (Linnaeus) Vahl].

Erect perennial to 1 m, with clustered stems; lvs 1.5-4.5 mm wide; glomerules 1-7, globose or subglobose (the lower spikelets ±reflexed), the terminal one 8-20 mm thick, the lateral subsessile or on peduncles to 2 cm; spikelets dark brown, 3-5.5 mm, the solitary fl terminal and perfect; bristles 6, about equaling the tubercle, usually retrorsely barbellate; achenes obovate- pyriform, 1.3-2.5 mm, two-thirds as wide, smooth, dark brown and somewhat concave near the raised margin, elevated toward the center into a prominent pale umbo; tubercle flattened, triangular-subulate, two-thirds to fully as long as the achene. Wet acid soil on the coastal plain; N.J. to Fla., La., and Cuba. Many authors maintain that R. microcephala Britton, with small, round-topped achenes 1.3-1.6 mm, small spikelets 3-4 mm, and smaller glomerules, not over 1 cm wide, should be distinguished from R. cephalantha proper, with larger, often truncate achenes 1.8-2.5 mm, larger spikelets 4-5.5 mm, and larger glomerules, some 1.5-2 cm wide.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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