Carrion-flowers and closely related greenbriers have different sex flowers on separate plants. This is the female upright carrion-flower. The female floweer head, at least in this population, was about half the size of the male. Pollination is actually by a variety of flies, bees, and beetles. I led a wildflower walk for Toledo Metroparks Sunday, and saw this in bloom. So I knew to go looking for it yesterday. Also finding smooth carrion-flower was a bonus.