This image shows a very small portion of a cotton flower magnified more than 500 times. The spike-covered orbs are cotton pollen grains stuck to the papillar surface of the stigma, a sticky surface with finger-like projections. The stigma is located at the very top of the pistil, which is the female reproductive structure of the flower.
Cotton can self-pollinate or cross-pollinate with the help of bees that transfer pollen between the flowers of different plants. If conditions are favorable, the pollen grain will germinate after it is stuck to the stigma and form a pollen tube, which extends through the tissues of the pistil. Once the pollen tube reaches the ovary, fertilization can occur.