SEXUAL DIMORPHISM IN THE JAPANESE SPECIES OF MACROMITRIUM BRID. (MUSCI: ORTHOTRICHACEAE)

Abstract

  Nine species of Macromitrium are recognized in Japan. Only M. reinwardtii Schwaegr. is monoicous, the others are dioicous. The eight species are dimorphic and produce dwarf males. Male dwarfness in anisosporous species is genetically determined, while dwarfness in isosporous ones seems to be regulated by phytohormones from female plants. Small spores of anisosporous Macromitria always produce the dwarf males. In contrast the male spores of isosporous Macromitria have the potential to develop into either normal or dwarf males. When single male spores of isosporous Macromitrium japonicum were cultured, they matured into the normal males. However, when the spores were sown singly on media with auxin (2, 4-D), dwarf males developed.