Definition of "antheridium"

Ascodesmis is a third type which might be derived either directly or through the erysiphaceous type from an endomycetous ancestor; the antheridium and oogonium are but little differentiated, but the latter is furnished with a trichogyne and becomes septate after fertilization; the ascogenous hyphae are few and the sheath simple.

2010, Helen Gwynne-Vaughan, Fungi: Ascomycetes, Ustilaginales, Uredinales, page 54