While I was studying for my Masters I wrote a paper on lichen and moss. Sadly I remember very little about the contents of the paper except a couple of points,

• Lichen are multi organism, or multi species of plants. This from Wikipedia,

is a hybrid colony of algae or cyanobacteria living symbiotically among filaments of multiple fungus species, along with bacteria embedded in the cortex or “skin”, in a mutualistic relationship. Lichens are the lifeform that first brought the term symbiosis (as Symbiotismus) into biological context.

• Both moss and lichen (I think lichen especially) like clean air to thrive.

I took these photographs yesterday of two tree trunks in our back garden. I am taking their coverage in both lichen and moss as a good indication of the good air quality that we have here.