spore-bearing structure development basidium development The process that leads to the development of basidium, a small, specialized club-shaped structure typically bearing four basidiospores at the tips of minute projections. The basidium is unique to Basidiomycetes and distinguishes them from other kinds of fungi. GO:0075313 biological_process Note that basidiospores and basidia are separate biological structures. The basidium is the structure that bear the basidiospores, but the development of the basidium is a different process than the formation of the basidiospores themselves. For this reason, GO:0034295 basidiospore formation and GO:0075313 basidium development are different terms and are not linked.