Gymnostomum calcareum Nees & Hornsch. and allied plants in Europe, North Africa and the Middle East

Abstract Gymnostomum calcareum Nees & Hornsch., G. viridulum Brid. and G. 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 of G. calcareum, the biseriate axillary and protonema-gemmae of G. viridulum,and the bistratose regions near the leaf margins, and nerve 50 μm wide, in G. mosis. Sporophytes are unknown in G. mosis. G. calcareum has a world-wide distribution, G. viridulum occurs in southern Europe, north Africa and the Middle East, and G. mosis seems to be confined to the Middle East.