New nomenclatural combinations are needed for some of the North American species of Asarum to bring their names in line with the current understanding of relationships in the genus and to provide correct names for a treatment in the Flora of North America. Asarum L., in the broad sense, is a genus of low herbs with creeping stems and a few cordate-reniform leaves. Its flowers have a radially symmetrical, three-lobed calyx, twelve or fifteen stamens, and six styles. Its fruits are fleshy capsules containing many flattened, cordate, arillate seeds. There are about 90 species in Asarum s.l. (Araki, 1953; Cheng & Yang, 1983). Most of the species are found in temperate Eastern Asia and the southeastern United States, but a few also occur in Europe, eastern North America, and the Pacific Northwest. It is the only genus in the tribe Asareae and appears to be related to the genus Saruma Oliver, a native of China. Since Braun (1861), a number of sections have been recognized within Asarum (Duchartre, 1864; Schmidt, 1935). These are based on the fusion of perianth, the presence of constrictions and annuli in the calyx, the position of stigmas, the length of the anther connectives, the position of the ovary, and the longevity of the leaves. Some of these sections have been raised to generic rank, probably because they appear distinctive within their regional floras. Hexastylis Rafinesque of the southeastern United States is one of these. Braun, Duchartre, and Schmidt recognized the same group of species as Asarum sect. Ceratasarum Braun. The classification of the species of Asarum by Araki (1953) clarified the similarities and differences between the sections. Araki recognized two subgenera in Asarum: subg. Asarum, distinguished by the sepals being free above the base and forming a pseudotube, and subg. Heterotropa (Morren & Decaisne) 0. C. Schmidt, distinguished by the sepals being fused into a tube. He placed section Ceratasarum (Hexastylis) in subgenus Heterotropa with sections Heterotropa (Morren & Decaisne) Braun and Asiasarum (Maekawa) Araki, and he placed the other North American species in subgenus Asarum. The recognition of Hexastylis as a genus has persisted in the southeastern United States, in part, because Blomquist overlooked Araki's classification when writing his influential revision of Hexastylis (Blomquist, 1957). Also, it is easy to distinguish the species of Asarum sect. Ceratasarum (Hexastylis) from Asarum canadense L., the only other species of Asarum in the eastern United States. Blomquist (1957) listed 11 characters that distinguish the groups in eastern North America. Extrorse stamens and bifurcate style extensions define the species in section Ceratasarum. The other characters cited by Blomquist are less reliable. The thick, variegated, glabrous leaves that help to distinguish Hexastylis in the southeast are similar to those found in many other species of Asarum subg. Heterotropa, and in Asarum hartwegii S. Watson, a species in subgenus Asarum native to northwestern North America. Asarum europaeum L., the type of Asarum and subgenus Asarum, has leaves that are evergreen, but not variegated. The tubular calyces are characteristic of all species in subgenus Heterotropa, and subgenus Asarum sect. Brevituba C.Y. Cheng & C. S. Yang is somewhat intermediate in having species with lobes that are fused at the base. Superior to partly inferior ovaries are also found throughout subgenus Heterotropa. Short, blunt extensions on the anther connectives and attenuated calyx lobes are found in many species of Asarum, though the tendency is for the extensions of species in subgenus Heterotropa to be shorter. Finally, short staminal filaments are also found in all sections of subgenus Heterotropa with the exception of section Asiasarum (Maekawa) Araki. Recognition of a broadly defined Asarum is in accord with some of the major treatments of the genus. Cheng & Yang (1983) used the broad concept of Asarum in their treatments of the Chinese species. Owhi (1965) and Hatusima & Yamahata (1988) used it in their treatments of the Japanese species. In addition, the recognition of a broadly defined Asarum is consistent with the generic concepts of the other large genera in the Aristolochiaceae (i.e., Aristolochia (Schmidt, 1935; Pfeifer, 1966; Ma, 1989), Thottea (Ding Hou, 1981)). With the recognition of Asarum in the broad sense, the following new combinations are necessary. NOVON 3: 225-227. 1993. This content downloaded from 157.55.39.30 on Thu, 26 May 2016 05:00:43 UTC All use subject to http://about.jstor.org/terms