Nutrition of Embryo Sac
The morphology of the ovule suggests that the chalazal end is the main route for the entry of nutrients. The funicular vascular supply ends at the base of the integuments. The nutrients reach the embryo sac via nucellus; often a patch of specialised tissue called hypostase is present in between the funicular vascular supply and the chalazal end of the embryo sac.
The hypostase is also presumed to have a role in nutrition supply. In some cases the nucellar tissue is completely consumed during the development of the embryo sac. The inner integument becomes a glandular endothelium, and absorbs nutrients from outer tissues and supplies them to the embryo sac. Because of its structural and functional similarity to anther tapetum the endothelium is also called integumentary tapetum.