Lichen  (Caloplaca aractina)

Biology

Lichens have colonised some very extreme habitats, including some of the coldest and hottest areas of the planet. They are incredibly hardy organisms, able to survive for years on the minimum of water, and growing almost imperceptibly slowly. If you examine the colonies that grow on tombstones, you can work out the age of some of these patches of lichen. Tombstones usually have a date on them revealing the year that the bare stone became available for colonisation.

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