Homosporous ferns produce sporophytes by intra gametophytic selfing, inter gametophytic mating, or apogamy.Gametangium ontogeny, genetic load, and ploidy affect the mating system of each species.
In this paper,we study the permanence of populations of a competing chemostat model in a polluted environment.Population control is also dealt with for the model without inter species competitionin.