Antheridial initiation in Onoclea sensibilis L., an advanced leptosporangiate fern, begins with the production of a small, wedge‐shaped cell within the anterior region of the vegetative cell. This is in contrast to previous reports claiming that the initials are formed by a localized protuberance in the cell wall of the vegetative cell (Campbell, 1886; Davie, 1951; Leung and Naf, 1979; Nayar and Kaur, 1971). The mature antheridium of Onoclea is composed of three uniquely shaped jacket cells surrounding spermatogenous cells. The two funnel‐shaped jacket cell walls are shown to form in a lateral circular manner. Except for the production of the antheridial initial cell, jacket cell formation in Onoclea proceeds in accordance with the classical concept of antheridial development in advanced ferns accredited in part to Atkinson (1894), Campbell (1886), Kny (1869), and Strasburger (1869). The classical concept has been contested in more recent years by Davie (1951), Leung and Näf (1979), and Verma and Khullar (1966).