Oh,Oh it looks like the Greenland Blog just will not end. These next two are about lichens - something we all can identify but few can say much about it.
Lichens are made up of a combination of a fungus and an alga. Although previously described as a symbiosis scientists now see the interrelationship of fungi and algae as a finely controlled parasitism in which the fungus is parasitic on the alga. The lichen forming fungi are able to capture the alga and put them to use to form a lichen. This benefits the fungus in that the alga cells carry on photosynthesis utilizing the sunlight to produce food especially sugar alcohols to supply the fungus allowing the formed 'lichen" to grow. The lichen is a composite organism which has plant-like properties but is not a plant. It is estimated that 6% of the earth's land surface is covered by lichens. Some lichens have been considered to be among the oldest living organisms. Their slow steady growth rate has been used to date events. By convention the scientific name of the lichen is the same as the fungus present and not the alga. Recent perspectives on lichens indicate that they are relatively self-contained ecosystems in and of themselves possibly with microorganisms living with the fungi, algae, and/or cyanobacteria making this a holobiont.
Below is rock tripe (Umbilicaria) which are black leathery-looking lichens which adhere to predominately no-calcareous rocks. Its growth form is called crustose which indicates that it grows on the surface with its edges curled looking like peeling paint.
On their trek across the barrens from the Hood River to Fort Enterprise the starving men of the Franklin expedition of 1819-1822 ate these lichens. As a result they were further weakened by nausea and diarrhea.The lichens contained not only rock particles but also high levels of acids which irritated their intestinal tracts. To make them edible would have required boiling them with several changes of water and adding baking soda to counter the acidity, steps that were not available to these intrepid hungry explorers.