Picture taken on the 18th February 2007 on an olive tree, Can Coll, Cerdanyola del Vallés, Barcelona.
It is one of the commonest lichens all around Europe, from the seaside to the mountains, although it prefers temperate climate.On trees, fences, rocks, even pebbles.
Foliose lichen, corticolous, lacking rhizinae, forming elegant rosettes, upper part from grey to bluish when rainy wether. Lobes hollow ("physodes"), wrinkled or flat, tips tend to ascend. Frequent lip-shaped soralia on the lobes tips and the thallus. Lower side from brown to black. Apothecia rare, but present in the picture.
Cortex K+ yellow
Medulla and soralia P+ orange-red.