Basidiospores are

Basidiospores are Sexual spores.
A basidiospore is a reproductive spore produced by Basidiomycete fungi, a grouping that includes mushrooms, shelf fungi, rusts and smuts.
Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are produced by specialized fungal cells called basidia.
These are typically single-celled (without septa), and typically range from spherical to oval to oblong, to ellipsoid or cylindrical.