genus Cladonia are cup lichens, which often grow in branching, bush-like shapes. Like other lichen, British Soldier Lichens are unions of an alga (Trebouxia erici) and a fungus (Cladonia cristatella), the latter of which provides the scientific name for the lichen. The alga photosynthesizes food, and the fungus provides structure. Lichens are very slow-growing organisms; this species only grows about two millimeters per year.
red coats since soldiers of the period wore a variety of headgear, much of it not red.
The Marvelous in Nature, Hiker's Notebook, and this site.