Tolmiea Torr. & A. Gray
Tolmiea is native to western North America. It was long thought to be a monospecific genus. Recent studies, however, have shown that two species should be recognized: an autotetraploid (T. menziesii (Pursh) Torrey & A. Gray) and a diploid (T. diplomenziesii Judd, Soltis & Soltis) (Judd & al. 2007). Both differ not only cytologically but also geographically and genetically. The former is larger in stature and probably the species that is widely grown as an ornamental, also in Europe. It has been recorded as an escape in Belgium.
The genus is morphologically similar and closely related to the genera Heuchera, Mitella, Tellima and Tiarella. Hybrids between Tolmiea menziesii and Tellima grandiflora have been reported from Washington (Soltis & Bohm 1985).
Literature
Judd W.S., Soltis D.E., Soltis P.S. & Ionta G. (2007) Tolmiea diplomenziesii: A new species from the Pacific Northwest and the diploid sister taxon of the autotetraploid T. menziesii (Saxifragaceae). Brittonia 59: 217-225. [available online at: https://www.researchgate.net/profile/Douglas_Soltis/publication/22532620...
Soltis D.E. (1980) Karyotypic relationships among species of Boykinia, Heuchera, Mitella, Sullivantia, Tiarella, and Tolmiea (Saxifragaceae). Syst. Bot. 5(1): 17-29. [available online at: https://www.researchgate.net/publication/237162727_Karyotypic_relationsh...
Soltis D.E. (1982) Heterochromatin banding in Boykinia, Heuchera, Mitella, Sullivantia, Tiarella, and Tolmiea (Saxifragaceae). Amer. J. Bot. 69(1): 108-115.
Soltis D.E. & Bohm B.A. (1985) Chromosomal and flavonoid chemical confirmation of intergeneric hybridization between Tolmiea and Tellima (Saxifragaceae). Revue canadienne de botanique 63(7): 1309-1312. [available online at: https://www.researchgate.net/profile/Douglas_Soltis/publication/23716250...
Soltis D.E., Judd W.S., Soltis P.S. & Elvander P.E. (2009) Tolmiea. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 8. Oxford University Press, New York-Oxford: 107-108. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=133093]