Talk about monobiotic diplontic cycle of algae

Fucus is a brown alga presenting a branched thallus (diploid sporophyte). At the tips of the frond, the receptacles bear many small cavities called conceptacles. Each conceptacle contains the gametangia (structures where gametes are produced) and sterile hairlike filaments called paraphyses. Some species develop male and female gametangia inside the same conceptacle, whereas other species have separate male and female conceptacles on separate thallus The female gametangia, oogonia, produce by meiosis haploid non motile female gametes (eggs). The male gametangia, antheridia, produce by meiosis haploid biflagellated (motile) male gametes (sperm). Eggs and sperm are released simultaneously into water; the eggs release a pheromone that attracts the sperm (chemotaxis). Fertilization occurs externally (in water), by oogamy. The fertilized egg settles to the substrate where it becomes attached. The zygote develops by mitosis a mature diploid sporophyte.