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(Map updated: 11 August 2009)

This will be among the first of the large crustose lichens the beginner will find in upland areas overgrowing siliceous rocks, mosses and trees. The granular-warted thallus (the texture of old tree bark) is a pale yellowish-grey, covered in similar coloured, dome-like soralia sometimes joining up to form a continuous crust. Thick upland crusts (when well-developed these can be lifted from the substratum with a small penknife) should be tested first with a small drop of fresh bleach. O. androgyna gives a C+ scarlet reaction. When growing on trees the crusts may be thinner, so here the bleach test is even more important. Flesh-coloured discs are frequent on well-developed specimens.

Key characteristics

• Thick, granular-warted crust reacting C+ scarlet, discs flesh-coloured
• Thallus and soralia: pale, yellow-grey.

Original text submitted by Vince J. Giavarini