Wikipedia notes: "The iris flower is of interest as an example of the relation between flowering plants and pollinating insects. The shape of the flower and the position of the pollen-receiving and stigmatic surfaces on the outer petals form a landing-stage for a flying insect, which in probing for nectar, will first come into contact with the perianth, then with the stigmatic stamens in one whorled surface which is borne on an ovary formed of three carpels."
Gordon Mortensen printed this color reduction woodcut using 23 press runs for 23 colors.
Mortensen commented on the process he uses: "Only one woodblock is used. On it an image is drawn in India ink. Before the first color is printed, any areas that are to remain unprinted (white or the color of the paper) are cut away from the surface of the block. Then an oil base ink is used to print the first color on all of the sheets of paper that are to be used for the edition and proofs.
After the first printing the block is again cut, removing any surface of the block that is to remain the first color in the finished print. After each subsequent color is printed, the block is cut, the process continues until the print is finished and most of the surface of the block is cut away."