Wikipedia
Cystangium
Cystangium is a genus of fungi in the Russulaceae family. The genus contains 32 species that are distributed in Australia and South America. Cystangium was described by American mycologists Rolf Singer and Alexander H. Smith in 1960.
The taxon is phylogenetically part of Russula and thus probably a synonym. However, it has not been formally synonymised yet and continues to be used by taxonomists.