Peltigera

Peltigera is a genus of approximately 100 species of foliose lichens in the family Peltigeraceae. Commonly known as the dog or pelt lichens, species of Peltigera are often terricolous (growing on soil), but can also occur on moss, trees, rocks, and many other substrates in many parts of the world. Most species of Peltigera have the cyanobacterium Nostoc as the dominant photobiont but some have the algae Coccomyxa. The presence of both a green alga and a cyanobacterium makes some tripartite; in this case they show cephalodium growths containing the third partner, Nostoc. Because of their ability to fix nitrogen from the atmosphere, such lichens are influential in soil composition and generation....read more on Wikipedia.