Description: Currently known from a single poplar tree in County Kerry, C. nigrescens is one of Ireland’s rarest lichens. Many previous records were errors for ‘bat’s wings’ C. furfuraceum which has numerous, cylindrical isidia spread along the ridges, but rarely has discs. C. nigrescens also has isidia (a fact that helps separate it from C. subnigrescens which lacks isidia entirely) but these are coarse and nodular. C. nigricans is usually abundantly fertile.

Key Identification Features:

• Discs common, isidia scattered, nodular, never cylindrical along the ridges
• On nutrient-rich bark; very rare, south-western Ireland.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Collema nigrescens at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Collema nigrescens at iNaturalist World Species Observations database.