"Sarah took a deep breath and set off along the passageway again. A clump of lichen on the gatepost opened its eyes and watched her go. The eyes, on tendrils, had an anxious look, and when she had gone some distance away the clump, swiveling its eyes toward each other, commenced to gossip among itself. Most of it disapproved of the direction she had taken. You could tell that from the way the eyes looked meaningfully into each other. Lichen knows about directions."
Source : Jim Henson, A.C.H. Smith (2014). “Jim Henson's Labyrinth: The Novelization”, p.49, Simon and Schuster