What does the filiform apparatus do at entrance into ovule?

In most cases the mature embryo sac contains 7-cells and 8-nuclei. The cells are arranged as egg apparatus (two synergid cell and one egg cell), a central cell with two nuclei and antipodal cells (3 in number). The synergid cells occur laterally to the egg cell. These cells are characterised by finger-like projections called filiform apparatus towards the micropylar end. Filiform apparatus is formed due to invaginations of cell wall into the protoplasm and is made up of pectocellulosic fibres evolved in non-cellulosic sheath. Secretion of chemotactic substances for the attraction of pollen tube during fertilization is the function of synergids. One synergid becomes degenerate during pollen entry into the embryo sac and thus, provides a way for entry of pollen tube into the embryo sac.