Botanical and Swedish physician born in Gävle 10 October 1757 and died in Vadstena on 14 August 1819.
Disciple of Linnaeus, to pursue his studies in the University of Upssala and carry out the thesis under his direction (of plant Aphyteia) was continuation of the Linnean tradition in his work. He worked as Professor of botany at Wadstena, small town in the province of Östergötland, and was a member of the Academy of Stockholm. He devoted all his research to the study of lichens, their description and subsequent structural classification. He divided this genus in other forty and set the number of hitherto known, more than 800 species, of which many remain current even today, as in the morphological terminology he used is still largely valid.
Linnaeus concentrated their research on the classification of plants, fact which was recognized after his death, in the world of Botany. His line was continued by a generation of botanists such as J. Hedwing and h. a. Schrader, sometimes following her and others beyond it, but only Acharius managed to bury the rational basis of their classification. He was the author of various works; his first important publication was Lichenographiae suecicae prodromus, published in 1798. The Swedish botanist still performed the classification based on the appearance of the stem, but, after further observations, arrived to establish a new system based on the structure. Using this method, Acharius was able to establish a number of new families and species. Its advances in this avenue of research were collected in later works such as Methodus (1803), Lichenographia universalis (1810) and Synopsis methodica lichenum (1814). For a time, Acharius maintained that lichens were not really about plants. Only since the advent of the microscopes could be refuted his theories on the matter. For decades after his death his principles were harshly criticized, especially by German specialists such as H.G. Floerke, G.F.W. Meyes and K.F.W. Wallroth. Despite these criticisms, within his generation of researchers Acharius enjoyed a great respectability.