How do the sperm nuclei in a pollen grain reach the egg nucleus in an ovule?

When they land on the style they begin to bore their way through the stigma all the way to the ovule.

Through the tube made by the tube nucleus of the pollen grain:

each pollen grain has two nuclei, one called generative nucleus which combines with the nuclei of the ovule, and the other called tube nucleus tube nucleus which forms a tube that penetrates the stigma till it reaches ovule then it degenerates.