Embryo Sac: The female gametophyte of angiosperms containing eight nuclei and seven cells including one egg cell and two synergids.
Pollen Tube: A tubular structure produced by pollen grains that delivers sperm cells to the ovule for fertilization.
Double Fertilization: A process unique to angiosperms where one sperm fertilizes the egg forming a zygote, while another fuses with polar nuclei to form endosperm.