Antipodal mosses: IX. Platydictya (Bryopsida, Hypnaceae)

A taxonomic and nomenclatural history of Platydictya Berk. is outlined and the genus is considered to be a member of the Hypnaceae. Platydictya densis sima (Card.) Robins., a species originally described from the Antarctic as Amblystegium densissimum Card. and considered to be endemic to this region, is briefly evaluated. It is shown that this species is identical to the ho larctic P. jungermannioides (Brid.) Crum which is now established as a bipo lar disjunct and is the only representative of the genus Platydictya in the Southern Hemisphere. Platydictya jungermannioides is very rare in Tierra d el Fuego and on South Georgia, whereas in the maritime Antarctic it is loca lly frequent, extending from the South Orkney Islands to Alexander Island. The austral plants of P. jungermannioides are described and illustrated and the regional and global distributions of the species are mapped. The ecolo gical requirements of the species in Antarctica are also described.