Order: Pertusariales Family: Pertusariaceae
Species: Pertusaria amara
Photos: On Oak and rock. Co. Cork and Co. Kerry, SW Ireland
Very variable. Thallus thick or thin, grey, +/- zoned at margins with punctiform soralia +/- regularly scattered over surface. Whitish farinose soredia with persistent very bitter taste. (Test with a few grains on moist finger.) Apothecia very rare.
Usually found on deciduous trees, occasional on conifers and rocks. Widespread throughout Ireland but most frequent in eastern half.
Soralia and medulla K-, C-, KC+ violet (fleeting), P+/- red, UV-
Positive taste test for oxalic acid is unmistakeable.
Similar: Pertusaria albescens, taste test negative.
Pertusaria amara January and November 2010