GeoGraph - photograph every grid square

A lichen - Rimularia furvella

This lichen was growing on a schist boulder beside a footpath above the shore (the boulder is located about 70 metres NW of NS3178 : Ardmore fault plane, and stands out from the rocks of the beach, almost all of which are composed of red sandstone).

Rimularia furvella is a lichen that grows parasitically upon other lichens on exposed rocks; distribution map: Link (showing that it is not particularly a coastal species).

Only the thick brown crust belongs to the Rimularia furvella; the grey lobes at the edges belong to the species that it is growing on. The brown crust is divided by cracks into smaller areas (called areoles). Through a lens, these areas, in turn, are seen to consist of densely packed rod-shaped outgrowths called isidia; compare: Link

[Within many lichen species, genetic variation gives rise to several distinct chemical races (or "chemotypes"), producing different chemical compounds. The chemotypes are often visually alike, requiring chemical tests — Link — to tell them apart. Rimularia furvella has a race that produces gyrophoric acid, and another that produces norstictic acid; the specimen in the photo is of the latter kind.]