Ultrastructure of multicellular dwarf males with external gametangium in Oedogonium macrandrium (Oedogoniales, Chlorophyta)

This is the first comprehensive ultrastructural study on dwarf males with external gametangia in the genus Oedogonium, from androspore germination to the liberation of mature male gametes. The ultrastructure of the process in O. macrandrium Wittrok is similar to that of Bulbochaete hiloensis (Nordstedt) Tiffany, but with two remarka- ble differences. In O. macrandrium : 1) instead of a true transverse wall, only condensed mucilage appears between the gametes of each antheridial cell, and 2) the cell wall between the basal cell and the basal most antheridial cell has sim- the cell wall between the basal cell and the basal most antheridial cell has sim- ple plasmodesmata similar to those present in the transverse walls of vegetative cells, which are absent in B. hiloensis.