Parnassiaceae Martinov. Grass-of-Parnassus Family.
A family of 2 genera and about 16 species, herbs, of largely north temperate and arctic areas. Numerous anomalous features separate Parnassia from the Saxifragaceae; affinities with the Droseraceae, Clusiaceae, Celastraceae, and other families have been historically suggested. It is now clear that its affinities lie with Celastraceae, but APG III’s (2009) and APG IV's (2016) inclusion of it in Celastraceae seems premature; it is here retained as separate. Considering the uncertainties of its relationships, Parnassia is best treated as a family, the Parnassiaceae, as suggested by numerous workers as early as 1821, and increasingly accepted in recent decades. The very distant relationship of Parnassia to the Saxifragaceae (sensu stricto) has been strongly reaffirmed by molecular analyses (Morgan & Soltis 1993, Soltis et al. 2000, Savolainen et al. 2000).
Ref: Ma, Ball, & Levin (2016) In Flora of North America Editorial Committee (2016); Simmons . [including LEPUROPETALACEAE] In Kubitzki et al. (2004). Show full citations.