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A lichen - Cladonia diversa

The lichen shown here was growing on top of a dry-stone wall. Like other Cladonia species, it has a two-fold structure, consisting of (1) leafy scale-like structures at the base, and (2) erect structures called "podetia".

In this species, the podetia have cups on top, bearing red fruits (these are not just masses of spores, but they do produce spores; some species produce red fruits, some brown fruits, while others rarely produce fruit at all). In C. diversa, the fruits sometimes merge to form a mass that completely fills the cup, as shown in this photo.

This species (listed under "C. coccifera" in older books) is very common in a variety of habitats, including "acid soil, rotting trees, heathland, sand dunes and soil pockets on walls in upland regions" ["Lichens – An Illustrated Guide to the British and Irish Species", Frank S. Dobson, 2005]. It appears yellow-green because of the presence of usnic acid (a substance which has occasionally been employed for its antiseptic properties).

At 6 on the Hawksworth and Rose scale (NS3778 : A lichen - Ramalina fastigiata), this species is moderately tolerant of atmospheric sulphur dioxide pollution.