Yellow Wall Lichen
The Yellow Wall-lichen, Thelochistes parietinus (L.) Norm.Habit and habitat.-On trees and rocks usually near bodies of water.
Vegetative organs (thallus).-Leaf-like, pale yellow to orange above, white below; loosely appressed to the surface on which it grows, the margins sometimes ascendant, not gelatinous when moist.
Fruiting organs (apothecia).-The disk orange, the margin (thalline exciple) entire.
Spores.-Colourless, ellipsoid, polar-bilocular.
Name.-The specific name parietina, is from the Latin parie (t-) s, a wall, referring to its habit of growing on stone walls.