In 1801, South African-born Dutch mycologist Christiaan Hendrik Persoon (1761–1836) wrote one of the first treatises on modern mycology. In 1821, the first extensive taxonomical study of fungi, Systemia Mycologicum, was published by Swedish mycologist Elias Fries (1794–1878)—a book that is still considered an authoritative resource on fungal taxonomy. He is also considered the “father of mycology” and devoted his career to the study of botany, concentrating specifically on fungi and lichens.