You know those lacey plants that hang in trees and look like long, strands of gray-green hair, you often see them next to the coast? A lot of people call that Spanish Moss. But it’s not, it is actually a kind of lichen called Old Man’s Beard or Lace Lichen. True Spanish Moss is only found in the southern United States. And believe it or not, it is actually a bromeliad, a member of the pineapple family, a highly evolved plant.
Lichens on the other hand are much more primitive. In fact lichens aren’t a plant, they are two, two, two plants in one. The green part is a kind of algae that does the photosynthesizing and makes all the food, the other component is a fungus that presumably provides structural support and helps retain nutrients and moisture.
To help remember this complex association naturalists have created a mnemonic device, Alice Algae took a lichen to Freddy Fungus and now they live together in a natural relationship. Cute, huh? Now it used to be thought that this was a mutually beneficial relationship but that’s wrong, the Alice algae can live just fine without the fungus but Freddy is apparently freeloading off of Alice.
There are many kinds of lichens and they grow nearly everywhere from the deserts and rainforests to even on the inside of rocks in desolate Antarctica valleys. There’s even a variety that grows of the back of beetles in New Guinea. They tolerate extremes of heat, cold and drought. They don’t get any nourishment from the substrate. Water and nutrients are brought in through the air. So not surprisingly lichens are very sensitive to air pollution, especially sulphur dioxide.
So one thing the maintenance workers don’t have to do is scrape the lichens off the Transamerica Building. If you have lichens growing near your house, rejoice the air around you is relatively pollution-free and that condition is unfortunately becoming more and more rare.
This Michael Ellis with a Perspective.