10. Rhynchospora chalarocephala Fernald & Gale, Rhodora. 42: 426, figs. 1, 2. 1940.
Plants perennial, cespitose, 30–100 cm; rhizomes absent. Culms erect to ascending-arching, slender, nearly terete, multiribbed. Principal leaves exceeded by culm; blades flat, linear, 1–2 mm wide, apex tapering, trigonous. Inflorescences: spikelet clusters 3–7, widely spaced, clusters loosely turbinate to hemispheric, to 1.3 cm wide. Spikelets brown to pale red-brown, lance-fusiform, 3–5.5 mm; fertile scales elliptic, 2.5–4 mm, acute, midrib short-excurrent. Flowers: perianth bristles 6, ± equaling tubercle. Fruits 1 per spikelet, (2.5–)2.7–3.3(–3.5) mm, body pale brown with yellowish center, ± broadly oblong-obovoid distal to stipe, lenticular, 1.5–2 × 0.8–1 mm; tubercle narrowly triangular subulate, (1–)1.2–1.5(–2) mm, less than 0.5 mm wide at base.
Fruiting summer–fall. Moist sands and sandy peats of savannas, acidic stream banks, seeps, flatwoods, ditches, and pond shores; 0–400 m; Ala., Del., D.C., Fla., Ga., La., Md., Miss., N.J., N.C., Okla., S.C., Tenn., Tex., Va.
Some specimens of Rhynchospora chalarocephala are very difficult to distinguish from R. microcephala, and unquestionably intergrades occur in peninsular Florida and the Gulf southern coastal plain. Rhynchospora chalarocephala tends to have longer, paler, narrower spikelets in looser clusters; the dilated part of the fruit body has a narrower, more oblong outline; and the tubercle is both narrower with a narrower base and longer (mostly 1–1.5 mm versus 0.9–1.2 mm in R. micro-cephala). Most material is easily sorted because R. chalarocephala has paler spikelets in turbinate to hemispheric clusters; the dark brown spikelets of R. microcephala are in globose heads.