Microscopic grains of pollen are discharged from the male organ of the flower. They contain the male gamete of the plant. The pollen is carried to the female part of that flower or another flower, where the process of fertilisation begins. The male gamete fuses with the female egg in the ovary of the flower. This image shows a diagram and a micrograph of a pistil.
Pistil micrograph, Li-Yu Chen, CC BY 4.0.