Order: Tremellales       Family: Tremellaceae Species: Biatoropsis usnearum Lichenicolous fungus. Photographs on Usnea subfloridana. Glengarriff, Co. Cork, Ireland. A very variable gall-forming basidiomycete, the four-celled basidia pale pink, reddish-brown, dark brown or black. Basidiospores are subglobose to ellipsoid with 1-3 transverse septa, 4.5-8 × 4-7.7 µm. The hyaline conidia are in rows, cells 3-5 × 2-3.5 µm. Parasitic on thalli of Usnea species, including U. flavocardia, U. florida and U. subfloridana, U. fragilescens and U. glabrescens. Similar: Biatoropsis hafellneri forms similar galls on the Usnea fragilescens aggregate, mainly on U. cornuta.

Biatoropsis usnearum on Usnea subfloridana. January 2010