The formation of vegetative cells from zoospores and the morphogenesis of the multilayered cell walls during this process was observed in some Trebouxia and Pseudotrebouxia species. In Trebouxia species, e.g. Trebouxia erici, the wall of the vegetative cell is formed around the zoospore while in Pseudotrebouxia species, e.g. Pseudotrebouxia corticola, firstly an autosporangium with its wall is formed then the autosporangium further divides.