Mnium is a genus of mosses in the family Mniaceae, placed within the order Bryales and the class Bryopsida (true mosses) of the phylum Bryophyta. The genus is distributed across temperate regions of Europe and North America, where its species typically colonise moist, shaded habitats such as woodland floors, stream banks, and rock ledges.
Members of Mnium are erect, leafy mosses characterised by relatively large, broad leaves with well-defined borders and distinct midribs — features that have given rise to common names such as "calcareous mosses" for several species. The leaf cells are large and clearly visible under a hand lens, and the leaf margins are often toothed. Sporophytes bear elongated, often drooping capsules on slender setae.
The genus currently comprises around ten accepted species globally. Recognised members include Mnium hornum (horn calcareous moss), Mnium marginatum (olivegreen calcareous moss), Mnium spinosum, Mnium thomsonii (Thomson's calcareous moss), Mnium stellare (stellar calcareous moss), and Mnium spinulosum (largetooth calcareous moss), among others.
Distribution
Mnium species occur in temperate regions of Europe and North America. They favour moist, shaded environments including woodland floors, stream banks, and calcareous substrates.
Taxonomy Notes
Mnium belongs to the family Mniaceae, order Bryales, class Bryopsida, within the phylum Bryophyta. GBIF records three accepted species in the genus. The genus name carries no authorship in GBIF, suggesting an early descriptive circumscription; formal nomenclatural attribution varies by treatment.
