<span>I'm assuming this in plants.
Brief-ish answer:
"Fertilization in plants occurs when pollen grains are transported from anthers to stigma. When ripe pollen from an anther catches on the stigma of the same kind of flower, each pollen grain sends out a small thread-like tube."
Here's a fuller answer:
"</span>Fertilization occurs after pollination, when pollen grains land on the stigma of a flower of the same species. During this time, a series of events take place leading to the formation of seeds. A pollen grain on the stigma develops a tiny tube that runs down the style of the ovary. The pollen tube contains a male gamete which meets the female gamete in the ovule. Fertilization occurs when the two gametes combine and their chromosomes join. The resulting product is a normal complement of chromosomes, with some from either parent flower. The fertilized ovule forms a seed, which consists of a food reservoir and an embryo that later develops into a new plant. In gymnosperms (conifers) male gametes are enclosed in pollen grains and are transmitted by wind or insects to the female reproductive organs. Fertilization in angiosperms (flowering plants) occurs when insects or other animals transport the pollen to the female reproductive organ (pistil).<span>
</span><span>Fertilization is the fusion of gametes to launch the development of a new individual organism. In animals, the process entails the combination of ovum with a sperm, leading to the development of an embryo. Fertilization in plants occurs when haploid gametes meet to create a diploid zygote, which eventually forms an embryo.</span><span>"
source: </span>https://www.reference.com/science/plant-fertilization-occur-ccf48c80e72fc410
