Although most lichens are shades of greenish or bluish grey, others are white, brown, black, reddish â even bright yellow or orange. These colours are caused by chemicals, often acids, produced by the fungal partner.
The bright orange yellow wall lichen Xanthoria parietina is a common, easily recognised lichen especially in nutrient-enriched sites. Look for it on trees and on many of the boulders in the Rock of Ages, where it benefits from the nutrient-rich droppings of perching birds.
