1. Pyrrhobryum Mitten, J. Linn. Soc., Bot. 10: 174. 1868. • [Greek pyrrho, flame-colored, and bryon, moss, alluding to peristome].
Stems with exterior cells in 2 or 3 rows, small, walls thick, interior cells larger, walls moderately thick. Leaves with base undifferentiated or occasionally indistinctly decurrent; margins double-serrate from near base; costal stereid cells well developed on both sides of guide cells; juxtacostal basal cells often weakly differentiated, short- to long-rectangular, enlarged, lax or not; medial and distal laminal cells uniform, isodiametric, rounded to 4-6-sided, smooth, walls thick; marginal cells 2-stratose. Seta wiry. Capsule striate and flared at mouth when deoperculate; exothecial cells hexagonal [quadrate- to rectangular-rounded], walls moderately thick, somewhat weakly collenchymatous at base; stomata few at base and in neck, superficial.
Species 10 (1 in the flora): se United States, Mexico, West Indies, Central America, South America, Asia, Africa, Pacific Islands, Australia; pantropical and southern temperate regions.
Pyrrhobryum is characterized by elongate stems, distal and spirally arranged, broadly to narrowly lanceolate or linear-lanceolate leaves with double-toothed, 2-stratose margins, costae distally toothed abaxially, laminal cells mostly isodiametric and similar to near bases, and sporophytes positioned somewhat midway on stems or at bases.
SELECTED REFERENCE Frahm, J.-P. et al. 2003. Synopsis der Gattung Pyrrhobryum (Musci, Rhizogoniaceae). Trop. Bryol. 24: 115-127.