Hylocomium Schimper in P. Bruch, W. P. Schimper, and W. T. Gümbel, Bryol. Europ. 5: 169. 1852.
Greek hylokomos, thick-grown with wood, indicating a deep forest habitat
J. R. Rohrer
Plants prostrate to more commonly arching-ascending with annual growth increments forming an ascending series of frondose tiers; growth sympodial, rarely appearing monopodial in reduced Arctic-alpine forms. Stems regularly (1--) 2--3-pinnate; paraphyllia numerous, branched from a multiseriate base into several, long, slender 1--2-seriate strands. Stem leaves somewhat differentiated, tightly appressed on stipe to erect among branches, oblong-ovate to ovate, lightly plicate, sometimes rugose in acumen, not decurrent; margins serrate to serrulate distally, serrulate to nearly entire proximally; apex abruptly narrowed to long, crimpled acumen, occasionally rounded, obtuse, or abruptly acute; costa double, extending 1/4--1/2 leaf length, or sometimes nearly absent; cells occasionally minutely prorate; alar cells not differentiated. Branch leaves smaller, erect-spreading, ovate to elliptic-lanceolate; margins broadly incurved near apex, reflexed at base; apex short acuminate, bluntly acute, or obtuse. Capsule inclined to pendent, mostly bent horizontal at neck; operculum obliquely long-rostrate from conic base; exostome teeth reticulate proximally on exterior surface; endostome segments with broadly elliptic perforations along keel, usually split wide open into one large gaping perforation.
Species 1: cool-temperate, boreal, and arctic regions, North America, Eurasia, n Africa, New Zealand, Australia.
