Identification key
algue
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Description
Thallus
Foliose, up to 3 cm in diameter, formed of small narrow lobes, thallus often not clearly visible because entirely covered with apothecia

Color
Upper surface yellow-orange (in the sun) to greyish (in the shade)
Reproduction
Apothecia: numerous, in tight groups that can cover and hide the entire thallus
Soralia: —
Isidia: —
Risk of confusion
Xanthoria parietina, a more common species, with much larger, conspicuous lobes and apothecia clustered towards the center of the thallus
Ecology
Substrate
Mainly on branch, sometimes on trunk or non-calcareous rock

Habitat
Heliophilous and nitrophilous

Occurrence
Common

Sensitivity to air pollution
Moderately sensitive to pollution