3. Calliergon megalophyllum Mikut. 圆叶湿原藓 yuan ye shi yuan xian
Bryoth. Balt. 34. 1908. Calliergon richardsonii var. megalophyllum (Mikut.) Meylan, Ber. Schweiz. Bot. Ges. 50: 497. 1940. Type: Europe.
Plants usually rather robust, dark green, glossy. Stems prostrate, up to 20–35 cm long, more or less pinnately branched; stem round or pentagonal in cross section, cortical cells small, somewhat incrassate, in 2–3 layers, central strand present; pseudoparaphyllia large, foliose. Stem leaves large, 5–6 mm × 4–5 mm, erect-spreading, concave, oblong-ovate, obtuse, abruptly narrowed, not or slightly decurrent at base; costae single, thin, extending to 4/5 the leaf length or subpercurrent; median leaf cells linear-rhomboidal, 40–70 μm × ca. 5 μm, shorter, wider toward apex, with well-defined apical cells; alar cells hyaline, inflated, round-hexagonal to rectangular, forming a sharply delimited group, usually extending across 1/2 the leaf base. Sporophytes not seen.