AbstractGymnostomum calcareumNees&Hornsch.,G. viridulumBrid. andG. mosis(Lor.) Jur&Milde are recognized as distinct species on the basis of their morphology and from culture studies. The best distinguishing characters are the elongated leaves ofG. calcareum, the biseriate axillary and protonema-gemmae of G. viridulum,and the bistratose regions near the leaf margins, and nerve 50μm wide, inG. mosis. Sporophytes are unknown inG. mosis. G. calcareumhas a world-wide distribution,G. viridulumoccurs in southern Europe, north Africa and the Middle East, andG. mosisseems to be confined to the Middle East.