Dr Leon Perrie
The sperm need to swim through water in order to get to the eggs, the eggs are housed or maintained in the gametophyte, and that dependence on water is why ferns are so often linked to wet habitats. If the sperm do manage to get to an egg, fertilisation occurs and that is where the two, the sperm and egg come together. That doubles the number of chromosomes and that gives rise to a whole new typical fern plant again and the cycle repeats.
Video: © University of Waikato
Archegonium image courtesy of Ohio State University