Wilfred B. Schofield

Plants large, in loose mats, dark green to golden, shiny. Stems suberect to ascending, , regularly pinnate; hyalodermis absent, central strand present, weak; pseudoparaphyllia foliose. Stem and branch leaves differentiated. Stem leaves squarrose, broadly ovate, , strongly plicate; base not decurrent; margins plane, sharply serrulate distally; apex acuminate; ecostate or costa short, double; alar cells differentiated, rectangular or quadrate; laminal cells smooth; . Branch leaves usually circinate-secund, pointing toward base (not underside) of main shoot, oblong-lanceolate, tapering to apex, plicate, 1-2 mm; costa double, short; laminal cells long-linear. Specialized asexual reproduction absent. Sexual condition dioicous; perichaetial leaves lanceolate, apex subulate. Seta red-brown. Capsule horizontal, cylindric, arcuate, contracted below mouth; annulus narrow; operculum long-conic; peristome double; exostome teeth striolate basally, papillose distally; endostome basal membrane broad, segments broad, keeled, cilia 2 or 3, nearly as long as segments. Calyptra naked. Spores spheric, smooth to finely papillose.

Species 1: North America, Europe, Asia; terrestrial habitats in temperate, boreal, and subarctic regions.

Ptilium is a remarkably elegant genus that is usually easily distinguished from Hypnum, as the plants have extremely plicate circinate leaves that curve proximally, toward the base of the main stem, not ventrally to the underside of the stem as those in Hypnum. The exostome teeth are red-brown and lanceolate; the endostome is pale yellow.

Lower Taxon

• Ptilium crista-castrensis (Hedwig) De Notaris