Types of Embryo:
1. Monosporic type: Develops from one megaspore. The normal type of embryo sac development has been studied in Polygonum by Strasburger. Since this embryo sac develops from one megaspore that is why this is a monosporic embryo sac. It develops from a chalazal functional megaspore.
Example: Polygonum
2. Bisporic type: Develops from the cell which is to form two megaspores. In this type, female gametophyte develops from one of two haploid diad cells, after the first meiotic division of the megaspore mother cell (MMC). One of the functional diad cells by the second meiotic division gives rise to two free megaspore nuclei which take part in the development of eight nucleate female gametophytes by the two successive mitotic divisions.
Example: Allium
3. Tetrasporic type: Develops from the megaspore mother cell soon after meiosis in its nucleus. In this type, all four megaspore nuclei take part in the formation of the gametophyte. After the meiotic division of the megaspore mother cell (MMC), all four free megaspore nuclei lie within the young embryo sac and undergo only one mitotic division to form the 9-nucleated mature embryo sac.
Example: Adoxa