Sepals and Petals and Stamens—Oh, My! Or, a brief discourse on putative homologies of perianth elements of Common Black Cohosh

I encountered some contradictory information while preparing to write the 2017 Wildflower of the Year brochure: some sources describe flowers of Actaea racemosa, Common Black Cohosh, as having petals, while others say petals are absent. How can that be? How could there be such uncertainty about this common plant, one known to science since before the time of Linnaeus? After a little research, I decided to describe Black Cohosh flowers as having a series of organs interpretable either as staminodes (nonfunctional stamens) or as petals located between its sepals and stamens (Figure 1). Frankly, I waffled on the petal issue, and this article explores wh