A macro shot of the interior of an Echinopsis spachiana flower, showing both carpels (center) and stamen (forming a ring around the carpels), making it a "complete flower", a term used in describing plant sexuality. Flowers, the reproductive structures of angiosperms, are more varied than the equivalent structures of any other group of organisms, and flowering plants also have an unrivalled diversity of sexual systems.Photo credit: Fir0002