A smut fungus on the ovaries of Primula farinosa (bird’s-eye primrose) in GB (also Primula stricta in Europe and China), which produces black powdery spore masses in seed pods. It can be found by squeezing apparently ripe seed pods – infected pods should leave black powder on fingers.
Sori developing in ovaries of the host, as black/brown powdery masses, visible when the seed pods open at their tops. Spores present in spore balls, completely enclosed within a layer (sometimes 2) of sterile cells which often collapse upon drying to resemble an enveloping membrane. Spore balls globose, ovoid to elongate, of 24-46 x 26-64 µm, each composed of (1-)3-15 or more spores. Spores globose, subglobose, ovoid to elongate or irregular, somewhat angular, 8-13.5 x 11-18.5 µm, medium to dark reddish brown. Sterile cells 5.5-13.5 x 6.5 x 20 µm, variable in shape, size, colour and wall thickness, globose, subglobose, ovoid, elongage, pyriform to irregular.
Description derived from Vánky, K. (2012). Smut fungi of the world. St. Paul, Minnesota: APS press.