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.
[1] Although variation exists, many mycobiont species have three layers.
The innermost layer is a loose web of hyphae.
The outer layer is composed of more densely packed hyphae and calcium carbonate microcrystals.
This article about lichens or lichenology is a stub.