More taken with oak trees.
All of the tree fungus shown so far have been on dead or dying trees. The fungus (it may be a lichen)in the last two photos of this group are on a what appears to be a healthy young tree. It resembles oak leaves but the green colour comes from algae on the surface. The underside is white.
Update -I googled
oak leaf lichen and got lucky. That's what it is called. I like it when things are named for how they look. If it was called Thompson's lichen or Stellers lichen, I'd still be searching.

It goes by many other names ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Quoting wikipedia ---- Lobaria pulmonaria is a large epiphytic lichen consisting of an ascomycete fungus and a green algal partner living together in a symbiotic relationship with a cyanobacterium—
a symbiosis involving members of three kingdoms of organisms. Commonly known by various names like tree lungwort, lung lichen, lung moss, lungwort lichen, oak lungs or oak lungwort. ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------