It was this stand of Swamp Maple that got me thinking about lichens. Below Wiki will fill in the details on just what a lichen really is. But to me, it is just so cool that two species get together and make life better for each, all the time not imposing on any other organisms. Sure, they grow on stuff, but for the most part they neither give nor take upon their supports.
Lichens are composite organisms consisting of a symbiotic association of a fungus (the mycobiont) with a photosynthetic partner (the photobiont or phycobiont), usually either a green alga (commonly Trebouxia) or cyanobacterium (commonly Nostoc). The morphology, physiology and biochemistry of lichens are very different from those of the isolated fungus and alga in culture. Lichens occur in some of the most extreme environments on Earth—arctic tundra, hot deserts, rocky coasts and toxic slag heaps. However, they are also abundant as epiphytes on leaves and branches in rain forests and temperate woodland, on bare rock, including walls and gravestones and on exposed soil surfaces (e.g. Collema) in otherwise mesic habitats. Lichens are widespread and may be long-lived; however, many species are also vulnerable to environmental disturbance, and may be useful to scientists in assessing the effects of air pollution, ozone depletion, and metal contamination. Lichens have also been used in making dyes and perfumes, as well as in traditional medicines.
"Lichen." Wikipedia, The Free Encyclopedia. 3 Dec 2009, 22:39 UTC. 5 Dec 2009 <http://en.wikipedia.org/w/index.php?title=Lichen&oldid=329551720>.