12. Isopyrum L.
Sixteen species,
North America, Europe, Asia.
Some authors
have treated the genus Isopyrum in a relatively restricted sense, with
several species groups segregated as separate genera (Tamura and Lauener, 1968;
Tamura, 1984, 1993). Among these, the eight species of Isopyrum in the
strict sense have basally attached, tiny, nectar-secreting petals. Species that
lack petals are then treated as the genus Enemion Raf., which includes E.
biternatum of eastern temperate North America, four species that are each
narrowly endemic in portions of the western United States and Canada, and one
eastern Asian species.