Answer:
The gills of a mushroom are the structures that produce the spores of the fungus (spores). When the mushroom is first formed, a basidium is a single cell that will eventually produce spores of the fungus. Following karyogamy (the fusion of two nuclei), a basidium is a cell with a single nucleus that will divide to produce spores. The basidium then undergoes meiosis, which produces four haploid spores that will eventually develop into spores of the fungus.