Following pollination, the pollen grain absorbs water from the stigmatic exudate and germinates to produce a pollen tube. In the life cycle of flowering plants, the pollen tube serves as a transient structural link between the end of the male gametophytic phase and the beginning of the sporophytic phase. As is well known, the pollen tube elongates in a seemingly endless extension of itself as it travels through the style to the ovary, seeks out the ovule, grows into the embryo sac, and discharges the baggage of sperm. The proportional increase in wall area that occurs during elongation of the pollen tube is by tip growth. Much of the work on the germination of pollen grains on the stigma and growth of pollen tubes in the style was considered in Chapter 7; however, this work does not tell much about the requirements for pollen germination and pollen tube growth and about the structure, growth physiology, and metabolism of pollen tubes. Indeed, with the insight gained from the knowledge of the complexity and diversity of the components of the stigmatic exudate in general, one can only wonder about the specific molecules that promote pollen germination and pollen tube growth. Therefore, it suffices to remark here that the emerging model of pollen germination on the stigma and of pollen tube growth in the style hardly does justice to the molecular mechanisms of germination and the dynamic processes of pollen tube growth.