Topic summary
Basidia

Extracted from the Wikipedia article Basidium.
Structure
Most basidiomycota have single celled basidia (holobasidia), but some have ones with many cells (a phragmobasidia). For instance, rust fungi in the order Puccinales have phragmobasidia with four cells that are separated by walls along their cross section. Some jelly fungi in the order Tremellales also have phragmobasidia with four cells that are separated by walls and are shaped like a cross. Sometimes the basidium develops from a probasidium, which is not elongated like a typical hypha. The basidium may be stalked or attached directly to the hyphae.