Erythea 8: 43. 1922.
Plants densely cespitose. Culms 35–75 cm. Leaves: sheath summits U-shaped, sometimes prolonged to 2 mm beyond collar; distal ligules 2.5–8 mm; blades 3–5 per fertile culm; 15–45 cm × 2–3 (–4) mm. Inflorescences ascending, dense, green to gold or brown, (1–) 1.4–2.5 cm × 9–17 mm; proximal internode 1.5–4 mm; 2d internode 1–4 mm; proximal 2–3 bracts erect to ascending, leaflike, the proximal longer than inflorescence, often more than 2 mm wide, base ± surrounding culm. Spikes 5–11, ± individually indistinct, ovoid to broadly ovoid, 7–13 × 5–9 mm, base rounded to acute, apex truncate to acute. Pistillate scales pale gold to redbrown, with pale to green midstripe, lanceolate to ovate, 3.3–4.8 mm, shorter and narrower than perigynia, margin sometimes white, 0.1–0.2 mm wide, apex acuminate to awned. Perigynia ascending to ascending-spreading, green, gold, or sometimes coppery, conspicuously 0–11-veined abaxially, conspicuously 0–8-veined adaxially, ovate to lanceolate, usually flat, 3.5–5 × 1.3–1.75 mm, 0.3–0.5 mm thick, margin flat, including wing 0.2–0.3 mm wide; beak usually gold or redbrown at tip, usually flat, winged, ± ciliate-serrulate or, sometimes, cylindric, unwinged, ± entire for 0.5–0.6 mm, (1.4–) 1.7–2.5 mm, abaxial suture inconspicuous or with white margin, distance from beak tip to achene. Achenes stipitate, ovate to obovate, (1.2–) 1.5–1.9 × 0.75–1 (–1.2) mm, 0.3–0.4 mm thick.
Phenology: Fruiting late spring–summer.
Habitat: Seasonally wet places, 0–1000 m
B.C., Calif., Oreg., Wash.
Carex unilateralis intergrades with C. athrostachya.
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