tetrasporic (from four megaspore nuclei) leading to various types of embryo sac development or megagametogenesis (Plate 7.4). Of the angiosperm species studied so far, the monosponc type megasporogenesis is most common (พillemse and van Went, 1984). Typical monosponc megasporogenesis leads to development of an embryo sac consisting of seven cells: the egg cell, two synergids, the central cell and three antipodal cells. This type of embryo sac is referred to as the 'normal' or 'Polygonum' type