Ochrolechiaceae Lepra amara (Pertusaria amara) Growth type crustose Chemical results: Soralia and medulla K-, C-, KC+ violet (fleeting), P+/- red, UV-. Soredia taste test positive for oxalic acid (persistent, very bitter) Common on deciduous trees, occasional on conifers and over moss on rocks Very variable. A grey thick or thin thallus, slightly zoned at margins. Punctiform soralia are +/- regularly scattered over surface with whitish farinose soredia. Apothecia very rare, asci 1-spored. Similar: P. albescens is more zoned at margins, KC-, taste test negative

Pertusaria amara
On Oak. Holton Lee, Dorset. October 2012