Grimmiaceae subfam. Grimmioideae
Plants acrocarpous. Stems erect, central strand present or absent. Leaves erect or distally curved, rarely crisped, broadly oblong ovate, ovate-lanceolate, or narrowly lanceolate; margins plane, incurved or recurved, entire to occasionally denticulate distally, costa entire distally, percurrent to excurrent, smooth, in transverse section semi-terete, occasionally terete, elliptical or reniform, with 2 or occasionally with 3–6 adaxial cells near base, usually not markedly larger than abaxial cells, often excurrent as a long awn, awn smooth to toothed but not papillose; laminal cells smooth, mammillose, or papillose; basal cells quadrate to elongate, straight to sometimes sinuous, rarely sinuose-nodulose, thin- to thick-walled, without spiral thickenings, hyaline along insertion or concolorous with more distal basal cells; mid leaf cells mainly quadrate, to short rectangular, often sinuose but not sinuose-nodulose. Specialized asexual reproduction absent or occasionally present as gemmae borne in axils of distal leaves or on leaf tips. Sexual condition autoicous or dioicous. Seta short to long, straight, arcuate, or sigmoid, smooth, one per perichaetium; vaginula with straight epidermal cells. Capsule usually erect, rarely pendent, immersed to long-exserted, symmetric to ventricose, ovoid, obloid or cylindrical, sometimes globose, smooth or distinctly striate; stomata present or absent; annulus persistent or deciduous; operculum mammillate to long-rostrate; peristome absent basal membrane, distinctly thicker and trabeculate on the abaxial side, entire or split distally. Calyptra cucullate, mitrate, or mitrate-campanulate, smooth or plicate, not papillose, covering operculum to entire capsule.
Genera ca. 8, species ca. 250 (5 genera, 81 species in the flora).
Species of Grimmioideae are separated from those of the Racomitrioideae by features of the peristome, leaf cells that are straight to sinuose, and awns that are smooth to toothed. The Racomitrioideae have leaf cells that are strongly sinuose-nodulose, and awns that are sometimes smooth but are often papillose. The leaf attachments of the Racomitrioideae are brightly colored whereas those of Grimmioideae are hyaline or concolorous with the rest of the lamina (except Grimmia leibergii and G. attenuata which are yellow or orange). All Racomitrioideae have a straight or slightly arcuate seta that can be either smooth or papillose. Their capsules are smooth or almost so. In Grimmioideae the seta can be straight, arcuate, or sigmoid and are always smooth; capsules range from smooth to deeply plicate.
|1||Columella usually attached to operculum and deciduous with it; calyptra small, covering only operculum, mitrate or cucullate, smooth; capsule immersed to emergent; seta straight; leaf margins plane to recurved.||Schistidium|
|1||Columella not attached to operculum; calyptra small to large, mitrate, cucullate or erose, smooth or plicate; capsule exserted, occasionally immersed; seta straight, sigmoid or arcuate; leaf margins plane, recurved, or incurved||> 2|
|2||Entire lamina beyond the base spirally inrolled; leaves muticous or with a hyaline apiculus of one or two cells, cucullate; known only from Alaska.||Indusiella|
|2||Laminal margins beyond the base plane, recurved or incurved but never inrolled; leaves usually awned, rarely muticous, rarely cucullate; widely distributed||> 3|
|3||Calyptra less than 1/2 length of capsule, cucullate or mitrate, smooth; awns on distal leaves usually shorter than lamina; perichaetial leaves enlarged or not.||Grimmia|
|3||Calyptra large, covering at least 1/2 of capsule, campanulate-mitrate, plicate; awns on distal leaves typically longer than lamina; perichaetial leaves enlarged||> 4|
|4||Stem leaves oval to ovate-lanceolate, keeled distally, plicate or not; distal lamina 1- or 2-stratose; plants olivaceous to blackish green; acidophilic.||Coscinodon|
|4||Stem leaves ovate to obovate, concave or only somewhat keeled distally, not plicate; distal lamina 1-stratose; plants yellow-green to dark olivaceous; calciphilic.||Jaffueliobryum|