Kendrick L. Marr Richard, J. Hebda and Craig W. Greene†
Plants sometimes with sterile culms; densely cespitose, often with rhizomes 1–3 cm long, 1–2 mm thick. Culms (10)12–35 cm, unbranched, smooth beneath the panicles; nodes 1–3. Leaves basally concentrated; sheathsand collars smooth or scabrous; ligules 1–2.5 mm, obtuse, entire to lacerate;blades (1)4–12 cm long, 0.2–0.4 mm in diameter, involute, abaxial surfaces scabrous, adaxial surfaces sparsely hairy. Panicles (1.5)1.9–5.7(7.5) cm long, 0.4–3 cm wide, contracted to open, usually dark purple, rarely straw-colored; branches (0.8)1.1–2(3.5) cm, smooth, spikelets usually confined to the ends of the branches. Spikelets(3)3.5–4.5(5) mm; rachilla prolongations about 2 mm, hairs 0.5–1 mm. Glumesrounded, midvein smooth or slightly scabrous, lateral veins obscure, apices acute to acuminate, rarely awn-tipped; callus hairs (0.2)0.3–0.6 mm, 0.1–0.2 times as long as the lemmas, sparse; lemmas (2.5)3–4 mm, 0.5–1 mm shorter than the glumes; awns 3.5–6 mm, attached to the lower 1/3 of the lemmas, exserted, bent, purple; anthers 0.9–2.5 mm. 2n = 28.
Calamagrostis muiriana grows in moist to dry, subalpine and alpine floodplain meadows, lake margins, and stream banks, at 2484–3900 m, in the Sierra Nevadas south of Sonora Pass in central California. It differs from C. bolanderiin having basally concentrated leaves.