Marine Animal Encyclopedia
Sea Ivory Ramalina siliquosa
Nutrient-poor siliceous rocks are the favorite habitat of gray lichens, such as sea ivory. This lichen is usually gray-green in color, with a brittle, bushlike (fruticose) structure and disk-shaped fruiting bodies, called apothecia, at its branch tips. Sea ivory cannot withstand being trampled or extensively grazed, and so it grows best on vertical rock faces, to which it sticks by a single basal attachment.