How do you change your computer screen from landscape to portrait setting? My son was playing with the computer and when I looked at the screen he somehow changed it to a landscape appearance rather than standard portrait.
Lichens have been described as dual organisms because they are symbiotic associations between two (or sometimes more) entirely different types of microorganism 1  -. a fungus (termed the mycobiont). 2  a green alga or a cyanobacterium (termed the photobiont).
You are correct in your observation that it is a mold growing on the trunks of your trees. But even more correct is that it is a lichen. Lichens are a combination of two distinct plants that have taken up living together to get benefits from each other. The first part of the symbiotic relationship is the blue-green algae that pair up with a fungus (mold) that can't produce its own food stuffs. The blue-green algae produce sugars and starches and amino acids that the fungus uses to grow, and the fungus provides a substrate for the algae to attach to and grow and prosper.