Crustose lichens form crusty blooms on the surface of rocks and soil — even roof shingles, according to the forest service. Gordon, who organized the event, Lichen in a Winter World ...

The three major types of lichens -- crustose, foliose and fruticose -- all grow on this tree branch. (Photo by MSU ...

Found on every continent, lichen is an extraordinary organism adapted to survive in every habitat except seawater. More than just curious growths on rocks and trees, lichen can endure extreme ...