Double fertilization is the fusion of one male gamete with female gamete (syngamy) and Other male gamete with dipioid secondary nucleus (triple fusion), ie, double fertilization = Syngamy + Triple fusion. Triploid endosperm is formed during triple fusion. Double fertilization is characteristic feature of angiosperms. Double fertilization does not takes place in algae, bryophytes, pteridophytes and most gymnosperms.