Our guide in Ketchikan, Alaska, mentioned that lichen is used for medicinal purposes, and is a favorite food of the many animals in the area including squirrels, black-tailed deer, and mountain goats...but what is a lichen? The stringy, almost web-like lichen on the trees in Ketchikan hung in great swaths over the branches.
The following from the U.S. Department of Agricultural --
You can think of lichens as fungi that have discovered farming. Instead of parasitizing or scavenging other organisms for a living (such as molds, mildews, mushrooms), lichen fungi cultivate tiny algae and/or blue-green bacteria (called cyanobacteria) within the fabric of interwoven fungal threads that form the lichen body (or thallus.) The algae and cyanobacteria produce food for the fungus by converting the sun’s energy into sugars through photosynthesis. Perhaps the most important contribution of the fungus is to provide a protective habitat for the algae or cyanobacteria. Thus, lichens are a combination of two or three organisms that live together intimately.