Archidiaceae Schimp., Coroll. Bryol. Eur. 5. 1856.
Gao Chien and Si He
Plants small, slender and soft, up to 20 mm high, usually perennial, gregarious to tufted, often on moist soils in open habitats. Stems erect, simple or forked due to innovations (often becoming prostrate stolons with erect branches in the following year). Leaves larger and more crowded above, sometimes in capitate clusters, erect to erect-spreading, sometimes falcate-secund, scarcely altered on drying, elongate, oblong or ovate to lanceolate, occasionally long-triangular, obtuse, acute, or acuminate; margins plane or narrowly recurved on 1 or both sides above the shoulders, entire to serrulate; costa subpercurrent to strongly excurrent, consisting of homogeneous, thick-walled cells; upper cells short to moderately elongate, quadrate to rhomboidal; basal cells thin-walled, subquadrate or short-rectangular, those at the margins often short and subquadrate. Monoicous. Perichaetial leaves somewhat longer than vegetative leaves and sheathing at base. Setae none; capsules terminal or lateral, deeply immersed, small, globose, pale yellow, indehiscent except by rotting or irregular rupture; exothecial cells in one layer, transparent, hexagonal, lax, thin-walled below, rather firm-walled above; stomata absent, peristome none, columella none; opercula not developed. Calyptrae delicate, as a torn membrane attached to the vaginula. Spores usually few, large, rounded to irregularly tetrahedral, pale to orange-yellow, very thick-walled, smooth or minutely roughened.
The family consists of a single genus, Archidium Brid.