Ramalina siliquosa, also known as sea ivory, is a tufted and branched lichen which is widely found on siliceous rocks and stone walls on coastlands round the British Isles, occasionally slightly inland. It grows well above the high-tide mark but is still very tolerant of salt spray. The branches are flattened and grey, and bear disc-like spore-producing bodies. It forms part of the diet of sheep in Shetland and on the coast of North Wales. It is found in Iceland where it has a conservation status of a vulnerable species.

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