spring avens, Geum vernum

Spring avens is sort of an odd fellow as Geum goes. It's the smallest flowered with petals as short as one millimeter. But it's the fruit that really sets it apart. Many Geum have pistils that forms hooks in fruit, making them part of the late season bur crowd. Spring avens has those too, but they are formed in a different way than all the others. Even after molecular studies there is debate about where species fit into Geum, and where to draw the lines between genera. It appears that spring avens is more closely related to the unhooked species like prairie smoke than to the other hooks. A case of parallel evolution, but from many of the same building blocks? There is also a short stem between the calyx and the cluster of seeds. No other species of Geum has that. Spring avens grows mostly in woods in AR, DE, GA, IA, IL, IN, KS, KY, MD, MI, MO, MS, NC, NE, NJ, NY, OH, OK, PA, TN, TX, VA, VT, WI, WV, and ON. Lenawee Co MI, 5/14/13. Rose family, Rosaceae.