Lichens
Lichens are composed of two quite different organisms that work together. It is a symbiosis between algae (and/or cyanobacteria) that provide the sugars thanks to the photosynthesis they perform (transformation of carbohydrate+water into sugar+oxygen thanks to sunlight and the presence of chlorophyl in the algae) and a fungus that provides structure to the organism.
Lichens are often long-lived, the size of a specimen being an indication of its age. They are good indicators for the quality of the air, and some thrive in very specific and uncommon environments. They take different forms: 'crustose' crusts on stones (like on old buildings in cities), fruticose branch-like structures, and follose moss-like organisms (like Reindeermoss).
Different types of lichens attracted our attention throughout Yellowstone and Grand Tetons, so we decided to collect some photos of these special living organisms.