The flowers of Lamium orvala provide a striking example of how flowers lure bees into the flower to be rewarded by nectar. In doing so they brush against pollen which is transferred from 'male' to 'female' flowers as the bee forages. Actually I'm not sure if flowers perceive themselves to be male and female as such but this is how botany describes the process!

 Speaking of bees here a few more on Geranium phaeum, Tellima grandiflora and Pulmonaria Opal...