We've been looking to see the flowers on this Helwingia japonica for almost a year. The sign says it's monoecious, which means we should see some female flowers, and I'd imagined I was seeing some, but the Photo of the Day writeup says the garden's two Helwingia are male. That writeup also says that the flowers are borne on the leaf itself. Some writeup said the leaf petiole and flower pedicel are fused to the point where the flower emerges. I don't know if that's saying the same thing or not. Here's a new link for an abstract of the Dickinson article. I'm guessing the triangular bits are petals and not sepals? Where there are 3 petals, there are 3 stamens between the petals; where 4 petals, 4 stamens.