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(Map updated: 11 August 2009)

This species belongs to a relic wayside lichen flora that also includes Caloplaca luteoalba and Bacidia incompta. Shaded trunks of elm were its main habitat. In Ireland, the species was last seen on an elm in County Clare several decades ago, so should be searched for. The extensive, smooth white-coloured thallus spotted with pink or yellow discs, each with a radially fissured surface ornamentation, will distinguish it.

Key characteristics

• Large, smooth patches of white thallus on shaded elms, ash or sycamore spotted with pink or yellow discs
• Discs frequent, to 1mm diam., when young, very like Petractis clausa (described elsewhere); spores three- to four-septate.

Original text submitted by Vince J. Giavarini