Finnish naturalist, Johan Magnus af Tengström was custodian of the University of Helsinki's museum of natural history. In 1816 he applied for docentship at the Finnish university (which was at that time located in the old capital, Åbo, which is now Turku), with the first part of a monograph on the genus Geum L. A year later he obtained his doctorate for a dissertation written on one chapter of Aetius' work on ascarids. Between 1817 and 1819 he undertook a great tour of Europe, visiting Sweden, Denmark, Germany, France and Switzerland in order to study.

When the university was moved to the new capital, Helsinki, he became an instructor in natural history. Apparently Tengström offered lectures on a wide range of themes, including cryptogamic plants, phytogeography and cell biology, but often did not deliver. He was, however, a fine public speaker and is said to have so impressed the Tsar Nicholas I with a speech given at the coronation celebrations, that he was named professor. Indeed, in 1841 he took over the professorship in botany and zoology from C.R. Sahlberg.

He did not publish any works other than those mentioned above and an essay entitled "De fructus in phanerophytis evolutione", which was used to support his application for professorship. This dissertation described the theory that the parts of a flower are all metamorphosed leaves. Tengström's main job while at the university was arranging and listing the plants in the herbarium collection (H). His lack of scientific activity was attributed to a nervous disorder which he suffered from and because of which the university consortium decided it was best if he resigned. Tengström did so in 1847.

Sources:
R. Colander, 1965, The History of Botany in Finland.