Monographs Details: Hypnum
Authority: Sharp, Aaron J., et al. 1994. The Moss Flora of Mexico. Part Two: Orthotrichales to Polytrichales. Mem. New York Bot. Gard. 69 (2)
Family:Hypnaceae
Scientific Name:Hypnum
Description:Genus Description - Plants small to robust, in soft, green, yellowish, or brownish mats or tufts. Stems creeping or ascending, rarely erect, in section elliptic, with a weakly differentiated central strand, regularly or irregularly pinnate; branches spreading or ascending, complanate to julaceous, usually hooked at the tips; pseudoparaphyllia subfilamentous or foliose. Stem and branch leaves slightly to strongly differentiated, usually falcate-secund, concave, ovate- to oblong-lanceolate, short- to long-acuminate, sometimes decurrent; margins plane, recurved below, or strongly recurved nearly to the apex, subentire to sermlate above; costa double, very short to comparatively long and strong; cells linear-rhomboidal to linear-flexuose, smooth, those at the basal angles small and subquadrate to rectangular or enlarged-oblong and hyahne. Dioicous (or autoicous). Perichaetial leaves oblong-lanceolate, short- to long-acuminate, smooth or plicate, subentire to sermlate above. Setae smooth; capsules suberect to horizontal, oblong-cylindric, ± curved; exothecial cells subquadrate to rectangular; annulus present or absent; operculum conic-apiculate to rostrate; exostome teeth subulate-acuminate, yellowish to brownish, cross-striolate below, hyaline and papillose above, bordered, trabeculate; endostome yellowish-hyaline, finely papillose, consisting of a high basal membrane, segments split along the median line, and cilia 1-3. Spores nearly smooth to papillose. Calyptrae naked.

Discussion:The genus is characterized by pinnate branching, more or less differentiated stem and branch leaves that are usually falcate-secund, and inclined, asymmetric, cylindric capsules with perfect peristomes.