In the archegonium of a fern, there is only one neck canal cell. The archegonium is a multicellular structure that is responsible for producing and protecting the female reproductive cells, known as eggs. The neck canal cell is one of the cells found in the neck of the archegonium that helps facilitate the fertilization process. It acts as a passageway for the sperm to reach the egg. The presence of only one neck canal cell allows for a more efficient transfer of sperm to the egg, ensuring successful fertilization.