Mystery green thing. What is it?

This is the time of year to look for lichens and tree fungi; when it's not too cold to stand still, admiring, and the leaves still haven't hidden them from view.

These are a few from that "spooky wood"*.

Staghorn lichen? Two different species? The one on the left is slender and spiky. And a flattened leaf lichen. On bark of a creek-side shrub.

More staghorn.

A leaf lichen on a twig. It looks like Parmelia (sulcata?).

And I don't know what to think of this next one. Is it a lichen or a shelf fungus? Or a lichen colonizing a shelf? (Click on the photo to see it full-size. What do you think?)

Mystery green thing.

And a common shelf fungus:

Iffy photo of the whole shelf. Too much white on top for the long-suffering camera.

Underside of a similar one on the same log.

Googling along, looking for holly-leaf lichen colonizing bracket fungi, a question caught my eye; "Why do lichens ..." And I had clicked away from it before I realized that it was the perfect question. Why do lichen take on so many disguises? Why do they eat rock? Why do they live on so many different suraces? Why do they change shape and colour from one week to the next?

1. To drive us amateurs crazy? or ...
2. To drive the professionals crazy, too? or ...
3. Because they can?

*The wood is not all that spooky in real life. It's a mini-bird sanctuary; the snags have been left purposefully. Eagles perch here, flickers, woodpeckers, assorted songbirds, and even a horned owl nest in the cavities in the broken and dying trees. Unfortunately, from the shade of the understory, the birds are black shapes against the sky. When they're visible at all, that is.

The lichens, at least, are at eye level.