The circumscription of Plagiomnium
used here follows Koponen (1968) which restricts the genus to those species of Mnium
sensu lato having plagiotropic stolons, macro‑ and micronemata, a Bryum‑type
stem epidermis, and unistratose bordered, singly toothed leaves (rarely entire
on the stolon leaves). Plagiomnium with 24 species in 5 sections (T.
Koponen 1968, 1981) is found throughout the world; the greatest concentration
of Plagiomnium species is in Asia. Koponen (1979) treated the genus for
Central and South America.