Snowball blossom

Snowball blossom
Lodged in the rumpled tissue of a Viburnum tinus stigma, pollen grains from other snowball blossoms (gray) swell with moisture. One (at center) is already growing the tube that delivers sperm to the ovule. Other species’ pollen (yellow and green) has landed amiss; genetic defenses exclude them from the fertilization race.

Image credit: Martin Oeggerli