The Papaveraceae occurs primarily in the northern hemisphere, but is also found in southern Africa and eastern Australia.  It has around 40 genera and 770 species, with Corydalis being the largest genus. 

Members of the Papaveraceae are herbaceous or softly woody plants in which the stems may have several rings of vascular bundles. All species have laticifers that produce a colored or clear sap.

The leaves are alternate and simple, but may be strongly lobed or dissected. Some are spinose.  The venation is pinnate. There are no stipules. 

The flowers are bisexual and radially symmetric in the Papaveroideae, bilaterally symmetric in the Fumarioideae. There are two sepals, but they tend to fall off early on, to the confusion of beginning (and not so beginning) students. There are usually four or six petals which generally look rather crumpled - as if they were dirty clothes that had been pulled out of the laundry basket. In the Fumarioideae, 1 or 2 or the outer petals may form a nectar spur or pouch.

The number of stamens varies from many, sometimes have petalloid filaments, to 6, in two groups of three, or even 4.  The pollen grains are tricolpate to polyporate.

The gynoecium consists of 2-many united carpels. The ovary is superior. with parietal placentation. The placentae sometimes intrude into the locule.

The fruit is a capsule, usually with many seeds but sometimes only 1-2.  The seed is sometimes arillate. This aril is NOT homologous with that of yew. Some arils in the Papaveraceae are attractive to ants, others to birds.  The most famous member of the family is probably the opium poppy, Papaver somniferum; the latex of other species does not, so far as I know, have the narcotic properties found in the latex of the opium poppy. Poppy seeds are obtained from the opium poppy, but they do not contain opium. 

The majority of North American floras treat the Fumarioideae as a distinct family, Fumariaceae, distinguished by having bilaterally symmetric flowers and stamens in two groups of three that are united by their anthers over the stigmas. It has, however, long* been recognized, that the genera involved were closely related to the Papaveraceae.  

*Even when I was a student

Arctomecon humilis

Argemone munita

Corydalis aurea

Dicentra uniflora

Dendromecon rigida

Dicentra cucullaria