The hyphae of rock inhabiting fungi are strengthened and better able to grow in crevices due to melanin pigments.
"Melanin pigmentation of rock-inhabiting fungi confers extra-mechanical strength to the hyphae that are then better able to grow into crevices (Dornieden et al., 1997; Sterflinger and Krumbein, 1997)." (Gorbushina 2007:1619)
Journal article Life on the rocksGorbushina, A. A.