sphaerocyst

— 1996, Mark Brundrett, Working with Mycorrhizas in Forestry and Agriculture, Australian Centre for International Agricultural Research, page 121, Russulaceae is distinguished from other families of mushroom-like fungi with gills by the presence of cells (swollen hyphae called sphaerocysts) and filaments which constitute the fruit bodies and can be observed under the microscope in the gill trama and other parts. All other families lack sphaerocysts.