Each basidium receives two different nuclei from hyphae of different sexes; these gametes, morphologically indistinguishable from each other, fuse to form a diploid zygote, which undergoes meiosis to produce four haploid spores. These are walled off from the basidium and expelled to germinate and give rise to new mycelia. Oomycota, or water molds, are the only fungi to have flagellated spores and to be oogamous, or
