As in all vascular plants, the sporophyte is the dominant phase or generation in the life cycle. The gametophytes of ferns, however, are very different from those of seed plants. They are free-living and resemble liverworts, whereas those of seed plants develop within the spore wall and are dependent on the parent sporophyte for their nutrition. A fern gametophyte typically consists of:

  • Prothallus: A green, photosynthetic structure that is one cell thick, usually heart or kidney shaped, 3–10 mm long and 2–8 mm broad. The prothallus produces gametes by means of:
    • Antheridia: Small spherical structures that produce flagellate sperm.
    • Archegonia: A flask-shaped structure that produces a single egg at the bottom, reached by the sperm by swimming down the neck.
  • Rhizoidsroot-like structures (not true roots) that consist of single greatly elongated cells, that absorb water and mineral salts over the whole structure. Rhizoids anchor the prothallus to the soil.