Growing on the trunk of a living oak tree, this lichen is quite hard and rough like sandpaper to the touch.
On Ilex opaca. I think P. cruenta is the correct species (bark rash lichen). Can anyone confirm?
black intertidal lichen on rock - 2nd photo of zonation with white Pertusaria above
Growing on bread.
On limestone rock at the summit of Black Mountain.
Medulla is black, perithecia sunken in areoles. Spores are 18-27 X7.5 um, simple, hyaline.
On Collema subflaccidum