Megaspore and female gametophyte (Figure 15.14A): The functional chalazal megaspore produces a multicellular female gametophyte or endosperm in the nucellus. Thus, endosperm is haploid and formed before fertilization in gymnosperms. two to five archegonia develop in the endosperm towards the micropylar end. A cavity called the archegonial chamber is formed in the endosperm near the archegonial necks. Each archegonium contains one haploid egg in the venter cavity.

Fertilization: The pollen tubes pass through the nucellus, reach the archegonial chamber and release the male gametes. A sperm enters the archegonium and fertilizes the egg to form a diploid zygote. If all archegonia are fertilized, 2 to 5 zygotes are formed in the ovule.