Part B of volume 2, covering subclass Dilleniidae, contains many economically and ecologically important plant groups, including Brassicaceae (mustard family), Salicaceae (willow family), Cucurbitaceae (cucurbit family), Violaceae (violet family), Malvaceae (mallow family), Frankeniaceae (alkali heath family), Loasaceae (loasa family), Primulaceae (primrose family), Hypericaceae (St.John's-wort family), Cleomaceae (cleome family), Elatinaceae (waterwort family), Tamaricaceae (tamarisk family), Paeoniaceae (peony family), Elatinaceae (waterwort family), Tiliaceae (linden family), Resedaceae (mignonette family), and Ebenaceae (ebony family). Included in volume 2B are 17 families, 119 genera, 463 species, and numerous varieties.