Carl Linnaeus brought order to the knowledge of plants and animals by arranging all known species in encyclopaedic
works. He proposed a system of plants, the sexual system, based on the number and arrangement of male and female
organs. His artificial sexual system has since long been replaced by ‘natural’ or phylogenetic systems but there has never
been a comprehensive comparison of the sexual system with modern plant classification. The currently most often used
classification of flowering plants is the APG-system. It is based on comprehensive phylogenies of flowering plants,
reconstructed by analyses of DNA data. The APG-system covers all flowering plants which are classified in 453 families
and these are classified in 45 orders. Most of the species were not known at time of Linnaeus. Families and orders in the
APG-system are arranged in larger informal groups representing major branches in the flowering plant phylogenetic tree.
Three such groups are the monocots, the rosids, and the asterids.
I have examined all genera published in Species plantarum (1753) and classified them according to order and major
groups in the APG-system. All classes except one, number 15 Tetradynamia, comprises groups of unrelated plants. Not
surprisingly, the sexual system does not display what we know today about plant relationships. As is evident from this
analysis, there is little correspondence between the sexual system and the APG-system. This does not mean that the sexual
system has been useless or misleading. When it was introduced, it formed the basis for much intensified research and
increased knowledge of plants.
2007. Vol. 25, 5-6 p.