How do flagellated sperm reach eggs in lower vascular plants?

In lower vascular plants—a group that includes ferns, whisk ferns, club mosses, spike mosses, and horsetails—the process of fertilization is dependent on the presence of water.1

These plants produce male gametes, known as antherozoids or sperm, within specialized sex organs called antheridia. Each sperm cell is equipped with flagella—whiplike hairs that allow it to move. When the antheridia rupture, these motile sperm are released and must swim through a film of external water to reach the archegonia, the female sex organs where the eggs are housed.231

The neck of the archegonium contains canal cells that break down as the structure matures, creating a pathway that permits the entry of the sperm to the egg located in the basal part of the flask-shaped organ. This reliance on water for the movement of flagellated sperm is considered a vestige of the aquatic ancestry of these plants.21