4. Physcomitrella Bruch & Schimp. in B.S.G. 小立碗藓属 xiao li-wan xian shu
Bryol. Eur. 1: 13 (fasc. 42. Mon. 1.). 1849. Phascum sect. Physcomitrella (Bruch & Schimp.) Sull. in A. Gray, Manual (ed. 2), 615. 1856.
Plants very tiny, yellowish green, somewhat glossy, scattered, gregarious or in loose tufts. Stems very short, 0.60–1.25 mm long, usually branched. Leaves contorted when dry, spreading when moist, obovate to elliptical, 1.8–2.4 mm × 0.7–0.9 mm, acuminate to acute at apex; lower leaves smaller, 0.9–1.2 mm × 0.3–0.4 mm; margins usually recurved, entire below, serrulate above, not bordered; costa slender, weak, reaching 2/3 the leaf length; leaf cells thin-walled, lax, upper cells irregularly hexagonal to oblong-hexagonal, slightly elongate below. Paroicous or synoicous. Setae thick, short, 0.4–0.6 mm long; capsules immersed, spherical or ovoid-spherical, ca. 0.4–0.5 mm in diameter, symmetric, bluntly apiculate at apex, indehiscent; opercula not developed; annuli none; peristome absent. Calyptrae very small, conic-mitrate, not or only slightly lobed at base, smooth. Spores subreniform, brownish, 17–19 µm diameter, densely spinulosely papillose.