Ever notice those greenish-gray-yellow spots on your tree branch, fence post or park bench? To some, it may look like a simple moss or mold and not worthy of a second glance. But if you did look closer, you'd realize it was something quite different and uniquely beautiful. Sort of like a big brooch or gaudy piece of jewelry, adorning that tree. What you were looking at is a lichen:
So what are lichens anyway? Lichens are composite organisms formed from algae and fungus that live in a symbiotic relationship. Together, the fungus and algae create a symbiotic relationship, living together as one organism, both inhabiting the same body.
According to The Backyard Nature Website, the fungus benefits from the algae because fungi, having no chlorophyll, can't photosynthesize their own food. A lichen's fungal part is thus "fed" by its photosynthesizing algal part. The algae benefit from the association because the fungus is better able to find, soak up, and retain water and nutrients than the algae. Also, the fungus gives the resulting lichen shape, and provides the reproductive structures.
Another important function of lichens is that they enable algae to survive in harsh environments where normally they cannot survive. Algae normally require water to survive, and yet in dry, sunny climates, they fungus can protect the algae and keep them from drying out (as long as there are occasional rain showers which allow them to recharge and store food).
AND - How about this cool fact: According to the US Dept of Agriculture, lichens have the ability to absorb everything in their atmosphere, especially pollutants. Lichens can provide humans with valuable information about the environment around us. Any heavy metals or carbon or sulfur or other pollutants in the atmosphere are absorbed into the lichen. Scientists can extract these toxins and determine the levels that are present in our atmosphere.
Pretty amazing stuff for something that most people may not even notice, huh?
Personally, I love finding these. I think they look like pressed flowers against the wood or rock. Looking closely, you can see the intricate shapes, the bumps, and ridges that almost resemble flower petals or fine lacework. Maybe you will spot them next time you are out for a walk!