The stones in the hedgerow on the 200 year old farm property we are working on have been sitting in the wall for such a long time that there are sections where the moss has started to grow over the joints. The rocks appear to be merging into one another.
Down through the centuries many stone cultures have attempted to create that same look — trying to fit the stones in their masonry structures so tight that the spaces disappear.
The Inca nearly accomplished it.
Perhaps moss is just another kind of civilization — a microscopic culture of tiny green masons striving, like the rest of us wallers, to make rocks look like they've melted into each other.