Endolithic lichen
An endolithic lichen is a crustose lichen that grows inside solid rock, growing between the grains, with only the fruiting bodies exposed to the air. An example is Caloplaca luteominea subspecies bolandri.
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Wikipedia
An endolithic lichen is a crustose lichen that grows inside solid rock, growing between the grains, with only the fruiting bodies exposed to the air. An example is Caloplaca luteominea subspecies bolandri.