These two branches of Usnea strigossa have so much interest for so little color. The lichens do not affect the branches at all. A lichen is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship. One absorbs water from the air and the other provides obtains the needed carbon dioxide from the air. The twig is simply a support.
This painting is currently part of the Philadelphia Watercolor Society Members' Exhibit.