Lichénologie

Lichenology is the branch of mycology that studies the lichens, symbiotic organisms made up of an intimate symbiotic association of a microscopic alga (or a cyanobacterium) with a filamentous fungus. Study of lichens draws knowledge from several disciplines: mycology, phycology, microbiology and botany. Scholars of lichenology are known as lichenologists. Lichens as a group have received less attention in classical treatises on botany than other groups although the relationship between humans and some species has been documented from early times. Several species have appeared in the works of Dioscorides, Pliny the Elder and Theophrastus although the studies are not very deep. During the first centuries of the modern age they were usually put forward as examples of spontaneous generation and their reproductive mechanisms were totally ignored. For centuries naturalists had included lichens in diverse groups until in the early 18th century a French researcher Joseph Pitton de Tournefort in his Institutiones Rei Herbariae grouped them into their own genus. He adopted the Latin term lichen, which had already been used by Pliny who had imported it from Theophrastus but up until then this term had not been widely employed. The original meaning of the Greek word λειχήν (leichen) was moss that in its turn derives from the Greek verb λείχω (liekho) to suck because of the great ability of these organisms to absorb water. In its original use the term signified mosses, liverworts as well as lichens. Some forty years later Dillenius in his Historia Muscorum made the first division of the group created by Tournefort separating the sub-families Usnea, Coralloides and Lichens in response to the morphological characteristics of the lichen thallus. After the revolution in taxonomy brought in by Linnaeus and his new system of classification lichens are retained in the Plant Kingdom forming a single group Lichen with eight divisions within the group according to the morphology of the thallus.