Primrose heterostyly. Image 1 of 2. Macro- photograph of a flower of the primrose Primula pulverulenta showing the "thrum-eyed" sex organ arrangement. This flower exhibits heterostyly, which means individual flowers of the same species show different arrangements of the sex organs. In this case, the anthers (blue), carrying the male pollen, are projecting from the vase-like flower's neck, with the female style tucked away deep in the flower. This formation is designed to inhibit self-pollination (thus promoting cross- pollination), as it makes it difficult for pollen to reach the style. For a specimen with the female style prominent ("pin-eyed"), see image B780/018.