A richly illustrated guide to lichens and their biologyExisting at the margins of life, lichens are the result of symbiotic relationships between fungi and photosynthesizing partners in the form of algae or cyanobacteria. Comprising more than twenty thousand species, lichens are pioneers in diverse ecosystems, colonizing virtually any surface and growing at almost any altitude. Found in rainforests, polar regions, deserts, and your backyard, lichens embody a parado...