Sexual reproduction in fungi usually involves two different
mating types. Because gametes of both mating types are about the
same size, they are not called male and female. Rather, one mating
type is called "+" (plus) and the other "−" (minus). When hyphae of
opposite mating types meet, they start the process of sexual
reproduction by fusing, bringing plus and minus nuclei together in
the same cell. After a period of growth and development, these
nuclei form a diploid zygote nucleus. In most fungi, the diploid
zygote then enters meiosis, completing the sexual phase of its life
cycle by producing haploid spores. Like the spores produced
asexually, these spores are also capable of growing, by repeated
rounds of mitosis, into new organisms.