Asarum sect. Asarum is a monophyletic group of 14 species distributed through North America, Europe, and Asia. The section is here treated in a taxonomic monograph based on morphological study of field-collected material and herbarium specimens. A key, descriptions, distribution maps, and citations of representative specimens are provided, and available information is reviewed on the pollination biology and phylogenetic relationships within the group. Six species of sect. Asarum are recognized in North America: A. canadense is widespread in the east, and the others range from widespread to narrow endemics in the west. Asarum canadense, which has at times been divided into several species or infraspecific taxa, is here recognized as a single species based on a lack of reliable differences among the variants. Asarum europaeum, which is the most widespread species in the section, has been similarly split historically, but also is treated here as a single taxon. In Asia, section Asarum consists of seven species from the eastern Himalayas through southeastern China, with two also extending into Japan.
Communicating Editor: Jeff H. Rettig