Authors: W. B. Schofield
Plants annual, minute, arising from a perennial persistent protonema. Stems erect, to 0.2 mm, completely enveloped in leaves. Leaves with costa weak or absent, brownish or with little chlorophyll, the exterior 0.2--0.4 mm, the interior to 1 mm, acuminate, ovate to oblong-lanceolate, margins entire to crenulate by bulging cells. Leaves with cells elongate-hexagonal to rectangular, thin-walled, 85--100 × 12--16 µm, smooth. Sexual condition functionally dioicous Perigonium of 3--6 perigonial leaves surrounding a few short antheridia and yellow, club--shaped paraphyses. Perichaetium also of a few brownish, weakly chlorophlyllose leaves, representing the plant. Specialized asexual reproduction by 2-celled starched filled rhizoidal gemmae. Seta erect, twisted to right when dry, 4--30 mm. Capsule wide-mouthed, 0.4--0.7 mm, pale to dark brown when mature, lacking stomata; annulus of 1--2 cell rows, deciduous; peristome of 16 reddish-brown to orange-yellow lanceolate exostomial teeth, to 0.3 mm, with vertical striations on exterior face, often with longitudinal perforations, endostome delicate and often discontinuous membrane, adhering to the exostomial teeth; operculum conic. Calyptra smooth, sometimes persistent on seta proximal to capsule. Spores 20--30 µm.
Genus 1 (1 in the flora): widely distributed in the Northern Hemisphere but always rare; North America, Europe, Asia; predominantly temperate, but also boreal and at lower elevations.
Shaw, J. and B. M. Allen. 1985. Anatomy and morphology of the peristome in Discelium nudum (Musci: Disceliaceae). Bryologist 88: 263--267. Duckett, J.G. and S. Pressl. 2003. Studies of Protonemal morphogenesis in mosses. IX. Discelium nudum: exquisite pioneer of unstable clay banks. Journal of Bryology 25: 241-245