I found this lichen (pronounced "liken") growing on the side of an old red oak tree. Lichen is a type of fungus that looks simple but is complicated. There are hundreds of kinds of lichens occurring the world over. Most of them survive in partnership with another similar organism that grows on or in the lichen performing photosynthesis and giving the lichen its color. Most lichens are shades of green, gray-blue, orange, red and yellow.
Many animals, especially herbivores, will eat lichen, although it is usually a food substitute. Other animals such as birds, mice, and even some insects use lichen by placing it inside nests for bedding or lining the outside of a nest for camouflage. Here in Southeast Missouri hummingbirds and wrens will often hide their nests by placing lichen on the outside of the nest where the lichen continues to grow.
The lichen shown here is a kind of foliose lichen sometimes called "lettuce" lichen because of its resemblance to lettuce. It grows in North America and is most often found in old growth forests. Lichens have the ability to thrive in some of Earth's harshest environments. Caribou eat lichen that grows on the cold Arctic tundra. Lichen can grow on the surface of a bare, flat rock in a hot desert.
Through the Woods is a weekly nature photo column by Aaron Horrell. Find this column at semissourian.com to order a reprint of the photo. Find more work by him at the Painted Wren Gallery.