Lobaria is a genus of lichens commonly known as "lung wort" or "lungmoss" as their physical shape somewhat resembles a lung, and their ecological niche is similar to that of moss. Lobaria are unusual in that they have a three-part symbiosis, containing a fungus, and an alga (as other lichens do), but also a cyanobacterium which fixes nitrogen.
Lichen have no roots, no leaves, no flowers. The fungus provides the basic structure, known as the thallus, and is adept at drawing minerals from the surrounding environment, as well as trapping water. The alga are individuals lodged in the fungus, and produce sugar from photosynthesis, using the water which it could not retain itself.
Navajo herbalists have described this mutually symbiotic relationship as "a marriage", and moss biologist Robin Wall Kimmerer describes this "marriage" as "Lichens are a couple in which the whole is more than the sum of the parts". 
Their sensitivity to toxins makes them an excellent indicator of ecosystem health. They are often found in ecological climax communities, such as the few remaining remnants of old growth forest in northwestern North America and Eurasia.
- Miadlikowska, Jolanta; et al. (2006). "New insights into classification and evolution of the Lecanoromycetes (Pezizomycotina, Ascomycota) from phylogenetic analyses of three ribosomal RNA- and two protein-coding genes" (PDF). Mycologia. 98 (6): 1088–1103. doi:10.3852/mycologia.98.6.1088. PMID 17486983.