There is a single granite shoulder above the second waterfall in the Edmund Gorge that I have been visiting for four years now, mostly without meaning to. The path takes you past it, and then a stone bench (not made by anyone — just a happy arrangement of two boulders) gives you a place to sit and look at it. The shoulder is roughly the size of a small car, and at any given moment it is wearing nine kinds of moss.
I had not, until this morning, learned the names of any of them. This struck me as a small disgrace. So I brought the field guide and a pencil and a thermos of black tea, and I sat on the bench for the better part of three hours and learned them, in the order the rock had arranged them in.
07:40 · From the waterline upClosest to the water, where the rock is wet all the time and a fine mist falls on it continuously, is a moss whose name is Hyocomium armoricum — a tight, glossy weave of green that looks almost like a small lawn. It cannot survive being dry. It is the most fragile of the nine and also, somehow, the most certain. It is doing exactly what it intends to do, every minute of every day, and it can do it forever as long as no one moves the river.
Just above it, where the rock is only wet when the river is full, is a moss called Racomitrium lanuginosum — woollier, longer-haired, almost grey at the tips. It looks like the shoulder is wearing a small fur. When you brush it with the back of your hand it is colder than the rock under it, even on a warm morning.
A rock that has nine kinds of moss on it is not a rock with mosses. It is, more accurately, a small map of how often things are wet.
The middle band.
Above the waterline mosses comes a band of Hypnum cupressiforme, which feathers across the stone in long, low rosettes, the colour of an old olive. It is the one most people would recognise as "moss." It is patient. It is everywhere. It is doing the bulk of the visual work on the shoulder, even if it is not the most interesting part of the story.
Inside the Hypnum, like jewels set into it, are small bright bursts of Polytrichum commune — taller, redder at the base, with little antennae of seed-bearing stalks that the wind moves separately from the rest of the moss. From a distance these look almost animal. They are the only one of the nine that the eye picks up as individual, rather than as a colour.
Above the middle band, where the rock dries out within an hour of any rain, the mosses get smaller and harder. There is a crust-like Andreaea rupestris, almost black, that I had previously mistaken for a stain. There is a tight rosette of Grimmia pulvinata with its small grey hair-tips, which look like the white roots of something you would not want to pull up. And there is, at the very top of the shoulder, a single patch of Cladonia — which is not a moss at all but a lichen, and which I include in the count because the rock seemed to.
What the rock was doing.
I had thought, before this morning, that the mosses were a decoration on the rock. By the end of the third hour I understood I had it backwards. The rock is a surface for the mosses. The mosses are using it — using its temperature, its angle, its capacity to hold water, the way it heats up at noon and cools at four. They are using the rock the way a person uses a south-facing window.
The whole thing is, in fact, a small economy. The waterline mosses produce a fine biological dust that drifts upward and feeds the band-mosses. The band-mosses break down slowly into the cracks and soften them, so that the high-rock mosses can get a foothold. Over a thousand years this softens the rock itself. The rock is, in a real sense, being slowly eaten — politely, in slow motion, by a committee.
I sat for another twenty minutes after I had finished writing, and finished the tea, and watched the rock being eaten. Nothing moved. Everything was moving.