Asexual reproduction involves germination of haploid spores, which divide by mitosis to produce hyphae cells.
Sexual reproduction (perfect stage) begins with release of pheromones by hyphae of different mating types; the cytoplasms fuse in a process called plasmogamy, producing heterokaryotic cells with haploid nuclei.
This is followed by karyogamy, or nuclear fusion. The diploid zygote is short-lived and undergoes meiosis, producing haploid spores.