In your textbook a group of plants are included in the Papaveraceae as subfamily Fumarioideae. These differ from the rest of the Papaveraceae in that they have clear sap, zygomorphic corollas, and 6 stamens. Dicentra spectabilis, bleeding-heart, is commonly cultivated; it is native to Japan.
Photo by K. R. Robertson, Mt. Airy Arboretum, Cincinnati, Ohio.