Embryo-sac in angiospermic ovule is homologous to

The angiosperm embryo sac (female gametophyte) and the fern prothallus are homologous structures because both represent the gametophyte generation in their respective plant life cycles. Both are haploid, produce eggs, and are the free-living or independent phase (though in angiosperms, the embryo sac is embedded within sporophyte tissue). The nucellus in Pinus is sporophyte tissue (part of the ovule), and the sporogonium of Funaria is the sporophyte generation.