Basidiomycota is a phylum of fungi (formerly the class Basidiomycetes), including the jelly fungus, the bird's nest fungus, the ear fungus, and mushrooms. They reproduce through sexual spores (basidiospores) produced by a specialized cell, the basidium. Basidia are cylindrical or club-shaped, often grouped to form the external fruiting bodies (gills) or bracket fungi, mushrooms, and puff-balls. Each basidium produces four spores.