Each megasporansium i.e. ovule is orthotropous and oval in shape. The mature ovule consists of a massive nucleus surrounded by a thick integument.
The integument is three layered; (sarcotesta) outer fleshy, middle stony (sclerotesta) and inner fleshy (sarcotesta). Nucleus is fused with the thick integument, except at the micropylar end, where it forms a beak-like structure, called the nuclear beak.
The pollen chamber lies within the nuclear beak. Pollen grains are collected in pollen chamber. Vascular supplies occur both in integuments and nucleus.
A single megaspore mother cell is differentiated within the nucleus. It undergoes meiotic division producing a linear tetrad of four megaspores (n).
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Out of the four megaspores, only the lowermost one (i.e. the megaspore facing towards the chalazas end) is the functional megaspore while the rest three degenerate.