It is heart shaped and called a prothalium. The prothalium is monoecious. While lying flat to the ground, rhizoids grow to anchor it down. On the ventral side of the prothalium, antheridia and archegonia begin to form. These mature at different rates to ensure cross pollination.
Antheridia sperm are multicellular and are aided by water to reach the archegonia.
Upon contact with the egg, fertilization occurs. As the zygote grows, it grows out of the archegonia and is dependent on the gametophyte for nutrients for a short while. After the sporophyte establishes itself, the gametophyte disintegrates. The gametophyte is not persistent, making the fern sporophyte dominant. As the sporophyte matures it is known as a crozier of fiddlehead.