The powdery substance that contains a flower’s male sex cells is pollen. More precisely, pollen consists of tiny pollen grains, each carrying the male gametophyte that produces sperm cells.
Pollen is made in the anthers, the pollen-producing parts of a flower’s stamens. When a grain lands on a compatible stigma, it germinates and grows a pollen tube down through the style toward an ovule. The tube delivers two sperm cells, one of which fertilizes the egg; the other helps form the nutrient-rich endosperm in flowering plants.
A common mix-up is calling pollen itself the sperm. Pollen is better understood as the transport package or male gametophyte, while the sperm cells are produced inside it. Wind, bees, butterflies, birds, and other animals can move pollen between flowers. Its often elaborate outer coating protects the genetic material during travel, and its surface patterns can help scientists identify plant species.
Pollen is also important beyond reproduction: fossilized pollen helps reconstruct ancient environments, while airborne pollen is a major trigger of seasonal allergies.