18. Rhynchospora nivea Boeckeler, Linnaea. 37: 527. 1872.
Dichromena diphylla Torrey; D. nivea (Boeckeler) Britton
Plants perennial, cespitose, 10–40 cm, wiry; rhizomes absent. Culms erect to spreading-ascending, leafy based, trigonous or compressed, ribbed. Leaves exceeded by scape; blades narrowly linear to filiform, 0.2–2 mm wide, apex tapering, trigonous. Inflorescences terminal, solitary, headlike, dense, white, leafy involucrate, hemispheric to globose, 0.5–1.5 cm wide; involucral bracts (0–)1–4, ascending to recurved, green, (0.7–)2–5(–6) cm × 0.2–2 mm. Spikelets white, ovoid, 5–7 mm; fertile scales several, boat-shaped, 2.5–3.5 mm, keel curved, not sharp. Flowers: perianth absent. Fruits 0.8–1 mm; body yellow to near black, broadly pyriform-obovoid, tumidly lenticular, 0.5–0.8 × 0.5–0.8 mm, margin narrow, flowing into tubercle; surfaces transversely sharply wavy rugose, ridges bordered by rows of fine, linear, vertical lattices; tubercle depressed triangular, lunate-based, short beaked 0.2(–0.3) mm, gray-crustaceous.
Fruiting spring–fall. Low, open, moist to wet, basic substrates of fens, meadows, seeps, and shores, limestone districts; 0–500 m; Okla., Tex.
Rhynchospora nivea, of the “Dichromena” of North America, is the smallest fruited and most slender and has the fewest and shortest involucral bracts (in some plants the bract is entirely absent). Involucral bracts of R. nivea are almost entirely green.