1. Diphyscium D. Mohr, Observ. Bot. 34. 1803.
[Greek di-, two, and physkion, little gut, alluding to double bladder of spore sac and capsule wall]
Plants gregarious, forming compact short turf. Leaves lingulate, costate, 1-2-stratose, distal cells chlorophyllose, quadrate to isodiametric, thick-walled and papillose or mammillose or smooth, proximal cells rectangular, hyaline, smooth. Perigonial leaves similar to vegetative leaves, except that interior are reduced and enclose paraphyses, axillary hairs, elongate antheridia. Perichaetial leaves long-awned with awn smooth or spinulose, awn often longer than lamina, with laminal apex lacerate and ciliate, when without sporangium strongly imbricate and penicellate, enclosing paraphyses, axillary hairs, few archegonia. Calyptra conic, barely covering operculum.
Species 12 (2 in the flora): North America, Mexico, West Indies, Central America, s South America, Europe, Asia, Atlantic Islands (Azores, Madeira), Pacific Islands, Australia.
Diphyscium is the most widespread genus in the family and is mainly temperate to subtropical. It is sufficiently distinctive and unlikely to be confused with any other genus in North America if perichaetia or sporophytes are present. Vegetative material is superficially similar to that of the Pottiaceae, especially in leaf form and papillosity. Fortunately, perichaetia and sporophytes are frequent in the eastern range of the genus, while turf firmly cemented by rhizoids is a trait not shared by Pottiaceae in the same range.
