Geolegnia helicoides. A. Androgynous antheridial branch, adjacent to the oogonium. B. Aspect of mycelium with immature and mature oogonia in clusters, and antheridial branches in water culture. C, D. Detail of characteristic diclinous and monoclinous coiling antheridial branches, around the oogonial stalks, oogonia and neighbouring vegetative hyphae. Bars: A and D = 10µm; B–C = 30 µm.