Sp. Musc. Frond. Suppl. 1(2): 1. 1816.
Plants medium-sized to large, in rigid tufts, green to brownish, glossy or dull. Stems irregularly branched, usually simple. Stem leaves ovate to ovate-lanceolate; base not cordate, occasionally rounded, not decurrent; margins plane to reflexed or revolute, entire; apex abruptly or gradually slender-acuminate; ecostate; alar cells quadrate, region large; laminal cells smooth or rarely slightly papillose distally over cell lumina; medial laminal cells oblong-rhomboidal to linear; apical cells smooth or papillose, or rarely so abaxially. Branch leaves imbricate, erect-appressed when dry, ascending to spreading when moist, ovate-lanceolate, somewhat concave, larger than stem leaves; margins plane to reflexed, entire or serrulate distally; apex acute to acuminate. Specialized asexual reproduction absent or by small, slender, caducous axillary branchlets. Perigonia axillary, gemmiform. Perichaetia on short, lateral branches, leaves strongly differentiated, greatly elongate, sheathing. Seta short to elongate. Capsule immersed to exserted, ovoid to pyriform; annulus cells in several rows, differentiated; operculum conic or oblique-rostrate; exostome teeth linear, papillose; endostome basal membrane low, segments imperfectly connate, papillose.
Nearly worldwide, except Australia and Oceania, temperate and warm regions.
Species ca. 30 (3 in the flora).
Leucodon is distinguished from the other genera in the family by its ecostate leaves and smooth calyptra. Forsstroemia is similar, but its plants are more glossy and the leaves are variably costate. Also, according to L. R. Stark (1985), paraphyses are present in the perichaetia of Forsstroemia but absent in Leucodon. In Leucodon, the axillary hairs are 3–5 per leaf axil, of two short proximal cells with brownish walls, and two or three longer distal cells. The stems are erect to spreading (or rarely pendent), straight or curved, and terete-foliate. The leaf apices are straight or falcate, sometimes filiform. The medial laminal cells are thick-walled and often porose. The calyptra is cucullate, or split on one side but gripping the seta below the capsule, and is naked. The exostome teeth are imperfect, perforate, and sometimes 2-fid.
|1||Leaves not plicate, not secund; apical laminal cells papillose abaxially; stems julaceous, short or rarely elongate; fragile branchlets in distal leaf axils absent.||Leucodon julaceus|
|1||Leaves ± plicate, secund or rarely so; apical laminal cells smooth or rarely papillose abaxially; stems not julaceous, elongate; fragile branchlets in distal leaf axils present or absent||> 2|
|2||Caducous branchlets absent; perichaetia, perigonia, and sporophytes common; leaves erect-appressed to secund; apical laminal cells smooth abaxially; terminal laminal cell concolorous to hyaline.||Leucodon brachypus|
|2||Caducous branchlets common, sometimes scarce or apparently absent; perichaetia extremely rare, perigonia and sporophytes unknown; leaves erect-appressed, rarely secund; apical laminal cells rarely papillose abaxially; terminal laminal cell hyaline.||Leucodon andrewsianus|