Umbels of strangely looking milkweed flowers. In addition to
reflexed calyx and corolla lobes, the unique flower of milkweed features a
crown, a structure formed by five petaliferous corolla appendages. These
are hooded. Each may have an additional outgrowth called horn. In clasping
milkweed the crown is pink. Stamen filaments are united in a tube enclosing
the style. Anthers are also united with each other and the stigma forming a
stigmatic disk. The surface that receives the pollen is hidden on the
lower side of the disk, covered by the united anthers.