Map Lichen and Phlox diffusa at Mt Townsend, Olympic Mountains, Washington, USA 17 Jun 2005 Rhizocarpon geographicum a form of crust lichen crustose See an interesting article on the use of lichens to measure the date of deposition. www.blackwellpublishing.com/Microbiology/pdfs/lichens.pdf yellow-green islands are areolae black fungal hypothallus at the margin. Note that there are other lichens on this rock, a whole little ecosystem Mt Townsend 17 Jun 05 mtt0617 024