Moss dwarf males (also known as nannandry or phyllodioicy) originate from wind-dispersed male spores that settle and germinate on the female shoot where their growth is restricted to a few millimeters. In some species, dwarfness is genetically determined, in that all male spores become dwarf. More often, however, it is environmentally determined in that male spores that land on a female become dwarf, while those that land elsewhere develop into large, female-sized males. In the latter case, dwarf males that are transplanted from females to another substrate develop into large shoots, suggesting that the females emit a substance which inhibits the growth of germinating males and possibly also quickens their onset of sexual maturation. The nature of such a substance is unknown, but the phytohormone auxin may be involved