Simpson's rosinweed, Silphium simpsonii

Simpson's rosinweed is a very unscientific presentation. These days most if not all authorities would include these plants in Silphium asteriscus as ssp. simpsonii. But I just couldn't resist another image of Silphium, and an excuse to wonder about its system. The disc flowers are functionally staminate. Only the ray flowers consistently produce seed. So each flower head only produces as many seeds as there are rays, instead of the dozens more they could have from the discs. What is the advantage of that? In any case it seems to work, and Silphium is spread across the continent. Simpson's rosinweed in some references is limited to FL, in others plants from AL, GA, and MS are included. Polk Co FL, 3/17/16. Aster family, Asteraceae.