Protonemata thalloid, with secondary filaments consisting of ± unbranched rows of cells with oblique dividing walls. Leafy shoots lacking rhizoids, consisting of erect main axis from which sprout fascicles of branches (in a few species there is only one much reduced branch per fascicle). Leaves ecostate, with two main types of cell. Elongate cells, dead at maturity, constitute a border. The main part of the lamina (except sometimes in perichaetial leaves) is composed of a mesh of two types of cell, chlorocysts, which are narrow and green, and hyalocysts, which are hyaline, inflated and dead at maturity of the leaf. Antheridia lateral, in leaf axils. Antherozoids biflagellate, with elongate body coiled in 2 turns of a sinistrorse spiral. Archegonia in groups of 1–5 at apex of a short specialised branch or the main stem. Setae absent, capsules joined directly to foot and exserted from perichaetium by elongation of pseudopodium composed of gametophytic tissue just below the archegonium. Capsules globose, urn-shaped when dry and empty, with a convex lid, lacking a peristome; exothecial cells brown at maturity, with scattered non-functional stomata; spore sac amphithecial in origin, overarching columella; calyptra a thin hyaline membrane, irregularly ruptured at maturity by growth of capsule. Spores arising in tetrads, each with a conspicuous triradiate scar on inner face.

There are two orders, Sphagnales and Ambuchananiales. The latter contains a monotypic genus, Ambuchanania, known only from Tasmania. The ordinal status of the Ambuchananiales is still uncertain.