A typical mature embryo sac of Angiosperms is a 7-celled and 8-nucleate structure.
(i) At the micropylar end, an egg apparatus is present which consists of an egg cell and 2 synergid cells. Synergids contain filiform apparatus which guides the pollen tube entry into the embryo sac during fertilisation.
(ii) At the chalazal end, three antipodal cells are present.
(iii) In the centre, two polar nuclei are present which get fused prior to fertilisation to form a diploid secondary nucleus.
Hence, 8 nuclei are constituted within 7 cells. Thus, embryo sac is 7-celled and 8-nucleate.
