Erik Acharius (10 October 1757 – 14 August 1819) was a Swedish botanist who pioneered the taxonomy of lichens and is known as the "father of lichenology." Acharius was famously the last pupil of Carl Linnaeus. Life Acharius was born in 1757 to Johan Eric Acharius and Catharina Margaretha Hagtorn in Gävle. He received a private education until he was admitted to Gävle Gymnasium in 1770. Later he matriculated at Uppsala University in 1773 where he studied natural history and medicine under Linnaeus and was the last student to defend a dissertation before him. Acharius's dissertation titled, Planta Aphyteia, was on a vascular plant species (Hydnora) collected in Southern Africa by Carl Peter Thunberg, which Linnaeus incorrectly classified as fungi. Thus he is known as "Carl Linnaeus last disciple" or the last pupil of Linnaeus. After graduating from Uppsala in 1776, he later worked for the Royal Academy of Sciences in Stockholm and completed his medical studies at Lund University in 1782. He was appointed town medical officer in Vadstena in 1785, district medical officer in Östergötland County in 1789, director of the new Vadstena Hospital (which he had initiated) in 1795, and titular professor in 1803. As a cartoonist, Acharius Johan illustrated Peter Westring's work Svenska lafvarne color history (1805) and Carl Peter Thunberg's Flora Capensis . In 1787 Erik Acharius married Helena Dorotea Scholander (1762–1804), the daughter of a trader, in Landskrona. After Helena's death Acharius married Margareta Maria Hoffberg on December 31, 1804. She was the daughter of Gottfrid Hoffberg who was in charge of production of saltpeter for munitions in Skänninge. In total Erik Acharius had four children, Lars Gustaf Acharius, Jean Torkel Acharius, Catharina Theodora Ohrling (née Acharius) and Charlotta Wilhelmina Acharius. Acharius spent the remainder of his life in Vadstena, where he died of a stroke while in his household garden examining a Spanish collection of lichens on 14 August 1819, at the age of 61. Work in lichenology Acharius belonged to the younger generations of Swedish botanists who continued what Linnaeus had left undone; classifying all living organisms. Acharius began the taxonomic classification of Lichenes and during his lifetime he classified over 3300 species of lichen separated into 40 different genera. At the time of Linnaeus's death all lichens were grouped into a single genus, thus Acharius was the first to expand lichen classification into the multi-divisional group of organisms it is known