But why should the primroses have such golden crowns? Plain green ones would protect the seed quite as well. Ah! now we come to a secret well worth knowing.1, Primrose with long pistil, and stamens in the tube. 2, Primrose with short pistil, and stamens at mouth of tube. (Diagram from Fairy-Land of Science) See also diagram here (scroll down to Primrose) and the photos and diagrams in this really good post about primroses and cowslips.
Look at the two primrose flowers, 1 and 2, and tell me how you think the dust (pollen) gets on to the top of the sticky knob or stigma.
Now the curious truth is, as Mr. Darwin has shown, that neither of these flowers can get the dust easily for themselves, but of the two No. 1 has the least difficulty.
But, as I have said, neither kind gets it very easily, nor is it good for them if they do. The seeds are much stronger and better if the dust or pollen of one flower is carried away and left on the knob or stigma of another flower; and the only way this can be done is by insects flying from one flower to another and carrying the dust on their legs and bodies.
(Photo found here--read the blog post too!)
A fun followup: The Magic School Bus, Episode 11: "The Magic School Bus Goes to Seed," (available as a book as well)