Lichen to get out

We had the faintest of sprinklings of snow this morning and it was soon gone. It's still brass monkeys though.

Spent a lot of the day cooking up a storm in the kitchen: a Walnut Frangipane and enough Bolognese sauce to feed an army! It keeps the kitchen warm.

I don't know much about lichens and mosses and other bryophytes. We have these cobble-stones (pavé) edging the garden beds. Some are covered in lichens and some have mosses but many have nothing?