More Lichens

I'm a bit hooked on lichens. On a walk last weekend, I thought I'd try to see how many species of trees might have lichens growing on them.

~ ~ ~ Black Cherry ~ ~ ~

~ ~ ~ Red Oak ~ ~ ~

~ ~ ~ Crabapple ~ ~ ~

~ ~ ~ Black Locust ~ ~ ~

So this morning on the ride to work I took the game a bit further when I asked if there was a tree without any lichens. I could not find one! Every single tree has some kind of lichen somewhere on the trunk or branches. How is it that I've never paid much mind to these little ones, organisms that seem exist everywhere yet remain somehow in the background? What else am I missing?