An order of flowering plants, division Magnoliophyta (Angiospermae), in the subclass Dilleniidae of the class Magnoliopsida (dicotyledons). The order has only a single family, the Diapensiaceae, with about 18 species of herbs and dwarf shrubs in temperate and arctic regions of the Northern Hemisphere. Within its subclass the order is marked by sympetalous flowers (flowers with the petals joined to each other by their margins, at least toward the base, forming a basal tube, cup, or saucer), separate pollen grains, and ovules that have a single integument (unitegmic) and are tenuinucellate (with the nucellus consisting of a single layer of cells covering the micropylar end of the embryo sac). Shortia and Galax genera are sometimes cultivated.