1. The megagametophyte is of the " Polygonum " type. 2. The megagametophytes of endosporic plants such as the angiosperms today. 3. The pollen tube proceeds to release the two sperm in the megagametophyte . 4. These would germinate to form microgametophytes and megagametophytes , respectively. 5. The megaspores become megagametophytes ( embryo sacs ). 6. This type of megagametophyte develops from the megaspore through three rounds of mitotic divisions. 7. The first seed plants, megagametophyte remains inside the megasporangium, attached to the parent plant. 8. Inside the ovary / ovaries are one or more ovules where the megagametophyte contains the egg cell. 9. Then, the megagametophyte is contained within a waterproof integument, which forms the bulk of the seed. 10. Since the protection of the megagametophyte is evolutionarily desirable, probably many separate groups evolved protective encasements independently.
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