Pollination is an important step in the reprouction of seed plants: the transfer of pollen grains (containing the male gametes, sperm) to the plant carpel of flowering plants, the structure that contains the ovule (which in turn houses the female gamete(s)), or directly to the ovule itself in gymnosperms. The receptive part of the carpel is called a stigma in the flowers of angiosperms. The receptive part of the gymnosperm ovule is called the micropyle. The study of pollination brings together many disciplines, such as botany, horticulture, entomology, and ecology. Pollination is important in horticulture because most plant fruits will not develop if the ovules are not fertilized. The pollination process as interaction between flower and vector was first addressed in the 18th century by Christian Konrad Sprengel.