Umbilicaria

Rock tripe is a common name for edible rock-dwelling lichens, especially species of Umbilicaria. The term is vernacular rather than taxonomic, and its scope has varied by region and source. In North America, rock tripe was known primarily as a famine food, eaten by Cree, Inuit, and other Indigenous peoples and later by European explorers and voyageurs during periods of extreme scarcity. In East Asia, by contrast, Umbilicaria esculenta has been valued as a delicacy in Japanese, Korean, and Chinese cuisine since at least the 17th century. The English name derives from the Canadian French expression tripe de roche. Rock tripe requires extensive processing, typically soaking and repeated boiling, to reduce bitter secondary metabolites such as gyrophoric acid that otherwise cause severe gastrointestinal distress. The principal carbohydrate in Umbilicaria is pustulan, which humans digest poorly, so the lichens provide less usable nourishment than their dry mass might suggest. They also conta......read more on Wikipedia.