Plants small, sometimes large, in tufts or loose cushions. Stems erect (creeping in O. kellmanii), branches erect to ascending. Leaves usually erect-appressed and straight when dry, spreading to wide-spreading when moist, ovate, oblong, lanceolate, ligulate, or linear-lanceolate, not rugose; margins entire or denticulate near apex; apex acute, acuminate, apiculate, or obtuse, awn absent (present in O. diaphanum); costa usually ending near apex; basal laminal cells elongate-linear or rectangular; distal cells usually rounded, almost isodiametric, 6-24 µm, papillose only over lumina, papillae 1-4 per cell, conic or 2-fid; marginal cells gradually shorter than basal. Sexual condition gonioautoicous or cladautoicous, rarely dioicous; perichaetial leaves similar to stem leaves or sometimes slightly differentiated. Seta to 6 mm. Capsule immersed, emergent, or exserted, globose to cylindric, smooth or 8-or 16-ribbed, sometimes constricted below mouth when dry; stomata superficial or immersed; peristome double, rarely single or absent; exostome teeth 0, 8, or 16, papillose or striate; endostome segments 0, 8, or 16. Calyptra mitrate, conic-oblong to short-conic, not split at base, smooth or papillose, ± hairy or naked, plicate (not or obscurely plicate in O. gymnostomum and O. obtusifolium), covering entire capsule. Spores isosporous.
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