a) A side view of the double and single Petunia flowers. Half of the sepals and petals were removed to reveal the inner organs. (b) Close-up of inner organs of double and single flowers after removal of all petals and several sepals. Note: stamens of single flowers and some stamens of double flowers were fused with petal organs; in double flowers the extraneous stamens were fused with the aberrant pistils, and the flower stalk, sepal and anther were thicker than in single flowers. Annotations: (1) stamen of double flower; (2) sepal (single and double flowers); (3) fused aberrant stamens and pistil of double flower; (4) pistil of single flower.