Description: When dry, this ‘aquatic’ lichen is easily told by its thin, black, broad-lobed, ragged-edged thallus growing on acid rock by streams or along the margins of loughs. The thallus is covered in a mass of tiny outgrowths (isidia) like little skin tags, later becoming flattened and scale-like. It will also grow on seepage rocks away from watercourses and on damp, mossy boulders in woodland. Frequent in the north and west of Ireland.

Key Identification Features:

• Thallus thin and almost papery with numerous isidia; on rocks and boulders by stream courses and on wet boulders in oceanic woodland
• Less distinctive and leafy when wet; an amphibious zone species.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Collema flaccidum at iNaturalist World Species Observations database.