The algal element of lichens is protected from UV radiation by a fungal skin.

References

"Others [lichens] develop minuscule branches and grow into dense curling thickets a few inches high. Their outer skin is formed by the compacted threads of the fungi and is sufficiently impermeable to prevent the loss of water from the partnership; beneath are the algal cells, kept moist and protected from harmful ultra-violet radiation by the fungal skin; and below them, in the centre of the structure, there is looser tissue, also provided by the fungus, where food and water is stored." (Attenborough 1995:216)

Book
The Private Life of PlantsBBC BooksFebruary 25, 2017
David Attenborough