Abstract
Flora of the genus Hypnum (Musci) in Japan comprises 19 species. The present report treats the history and general morphology of the genus; keys to Hypnum and ten allied genera of the same family (Hypnaceae), to the Japanese species of Hypnum，and to seven sections of Hypnum known in japan; and description, illustration, ecology, distribution and diagnostic characters of four species, H. calcicolum, H. callichroum ssp. japonicum, H. cupressiforme (var. cupressiforme, var. filiforme, var. subjulaceum) and H. densirameum.
