The Iris has an Ingenius Mechanism
The stigma of the iris has a little lip under the unique petaloid pistils, adjusted in just the right way to scoop the pollen off the back of a bee as it enters the flower, or from the head of a humming-bird. The bee or humming-bird will come in contact with the pollen of this flower only after it has passed the pistil, and the protecting shelf prevents the deposit of pollen as the insect or bird leaves the flower. It is a most ingenius and interesting arrangement.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 10 Chapter 2