Traditionally, it has been generally understood that the family Asclepiadaceae (the milkweeds) was derived from an ancestor within the family Apocynaceae. The two familes share numerous features, such as usually opposite or whorled leaves, a strong tendency to milky sap, bi-carpellate follicular fruits, winged or plumose seeds, etc. The molecular systematists have recently independently discovered this fact - that Apocynaceae is rendered paraphyletic if Asclepiadaceae is recognized. We follow this modern placement here. Thus, two genera formerly placed in Asclepiadaceae in our flora (the native Asclepias and introduced Vincetoxicum are now placed in the broader Apocynaceae. |