6. Pyramidula Bridel, Muscol. Recent., suppl. 4: 20. 1818.
[Latin pyramis, pyramid, and -ula, diminutive, alluding to calyptra]
Plants very small, gregarious or loosely caespitose. Stems to 1 mm, erect, rarely branching, Leaves somewhat crisped when dry, erect-spreading when moist, ovate to oblong, concave, 1.5-2.5 mm; margins entire; apices acuminate; costa single, percurrent, filling most of acumen; proximal laminal cells rectangular, distal cells short-rectangular to hexagonal. Specialized asexual reproduction by occasionally stalked, spherical, dark purple rhizoidal tubers. Sexual condition autoicous. Seta erect, to 1.5 mm. Capsule stegocarpous, erect, mostly exserted, globose and mostly urceolate following dehiscence, sharply constricted to neck, to 1 mm, wrinkled when dry, neck short, abruptly narrowed to seta; exothecial cells thin-walled, irregular in shape except for narrowly rectangular suboral cells; stomata with single guard cell, restricted to neck, superficial to rarely somewhat immersed; annulus none; operculum plane; peristome absent. Calyptra long-persistent, large, enclosing entire capsule and seta, four-angled, beaked, opening by longitudinal slits for nearly entire length to the clasping base. Spores spherical to angular, smooth.
Species 1: c United States, Europe, Africa.