English: Lichens on a boulder in a disused quarry. Several species of lichen can be seen here growing upon the top of a large upright boulder in a disused sandstone quarry (the quarry is shown here: 1050247).

The colourful orange-yellow lichen is the very common species Xanthoria parietina, which is a familiar sight on rocks and trees. Though brightly coloured here in its well-exposed location, it can be almost green when growing in more shaded locations, or when wet. It is common "on nutrient-rich trees, rocks, and walls, especially bird-perching sites" [F.S.Dobson, "Lichens - An Illustrated Guide to the British and Irish Species"]. A close inspection shows the lobe margins to be free of the rock, a feature that distinguishes this lichen from some otherwise similar Caloplaca species, in which the lobe margins are firmly bonded to the rock.

Left of centre is a pale lichen with small red-brown discs. This is Lecanora campestris. Like the previous species, it is common in nutrient-enriched sites. Since the boulder on which it is growing is tall and post-like, with a clear view, and with open space all around it, it is quite likely that it is indeed used as a bird-perching site; this would make the top of the boulder rich in nitrogenous nutrients.

Appearing in the centre of photo, to the upper left, and to the lower right (where it is encircled by the yellow lichen), are some small patches of another species, Physcia adscendens. As can be seen through a hand-lens, the ends of its lobes are hood-shaped and are fringed with dark-tipped hair-like structures called cilia. For a closer look at a more extensive patch of this species growing on the same rock, see: 1050283. This species is common on tree bark and on rock. (There is a very similar species called Physcia tenella, which has the same dark-tipped cilia, but whose lobe ends are curled back - 1066760; oddly, where fragments of the two species occur together, they can merge to form a vegetative or "mechanical" hybrid combining the characteristics of both species [George Baron, "Understanding Lichens"], and some even consider the two to be a single species.)

For other lichen species found in the same disused quarry, see: 1042725 and 1037581.