Nature CloseUp
by John Gallagher, Potato Creek State Park
Although lichens are all around us, most of us pay no attention to these unassuming little organisms. After all, they grow in places you wouldn't expect to look, like rocks, tree trunks, logs, sand, and bare soil. But if you were to look for them, they are easy to find because they occur in virtually all habitats and tolerate a wide range of environments. They have special adaptations that enable them to survive long periods of time without water and resist extreme temperatures. Lichens are true pioneers, able to establish themselves on barren surfaces in some of the most inhospitable places in the world. Unfortunately, lichens are very sensitive to air pollution. Their disappearance in many urban areas has been an early indicator of poor air quality.
Believe it or not it was Beatrix Potter, the author who brought us Peter Rabbit, who helped uncover the nature of lichens. Before becoming famous with The Tale of Peter Rabbit, Potter was a scientific illustrator, drawing and painting incredibly accurate and detailed pictures of fungi and lichens. Eventually she became quite knowledgeable about her subjects and began formulating her own theories. Although many scientists at the time believed lichens to be made up of an alga and a fungus, it was Beatrix Potter who proposed the idea that they shared a mutualistic relationship, that is, two organisms that help and need each other to survive.
Years later scientists proved that Potter was right about the symbiotic relationship between the algae and the fungi that make up lichens. The body of a lichen is made up of fungal filaments. Living among those filaments is either a green alga or a blue-green bacterium. The fungus delivers water and minerals to the alga, while the alga takes care of photosynthesis, making sugars to feed them both.
Lichens exhibit an amazing diversity of forms and colors. They are commonly classified into three different growth forms: crustose, foliose 
and fruticose. A crustose lichen is crusty, growing tight against the substrate and may be embedded in it. A foliose lichen is leaf-like, often lobed and attached only in spots. The shrubby, fruticose lichen is free standing with branching tubes that can be either upright or hanging.
For more information about lichens, visit an Indiana State Park or Reservoir interpretive center. Then grab a magnifying glass and go looking for these amazing little organisms. They can be found year round on rocks, tree trunks or fence posts just about anywhere the air quality is good.
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