Plants 0.5-3 cm, in loose, slender tufts, yellowish green to green, not tomentose. Leaves 3-4 mm, erect-patent when wet, appressed when dry, lanceolate, narrowed into a short, straight subula; margins entire below, faintly serrate at apex; apex of leaf serrate at back; alar cells hardly differentiated, only slightly larger than the basal laminal cells; basal laminal cells thin-walled, hyaline, rectangular; distal laminal cells short, subquadrate; costa filling 1/2-2/3 of leaf width, excurrent in a short concolorous apex, in transverse section showing adaxial hyalocysts that are 1/3 as wide as the costa, without abaxial stereids, ribbed at back. Specialized asexual reproduction by deciduous stem tips. Sporophytes not known in North America [rare elsewhere].