Lichens are the product of a unique symbiotic relationship between a fungus, and either a green algae or a cyanobacterium. In this association, the fungal member is termed the mycobiont while the algal component is termed the photobiont.
Lichens obtain their energy through photosynthesis by the photobiont, sugars produced by the photobiont are then absorbed by the mycobiont as its food source. In exchange, the fungal cells form a protective layer that screens the photobiont from damaging ultraviolet radiation, and aids in water retention. Because of this, lichens are able o survive in some of our most inhospitable environments, such as exposed, wind-swept rock faces and monuments.
Park staff currently have no data on the lichen species that occur within the George Washington Memorial Parkway, however inventories of this group are currently underway in Great Falls Park.