Megasporogenesis and Development of the Embryo Sac of Allium cernuum

1. The megasporangium of Allium cernuum is essentially like that of Lilium. 2. The archesporium arises directly from a hypodermal cell about 3 or 4 days before the flowers emerge from the bud. 3. The megagametophyte is formed from the chalazal dyad. The micropylar dyad disintegrates without further division. 4. The chalazal dyad undergoes three divisions, resulting in an eight-nucleate megagametophyte. 5. The mature megagametophyte consists of a large vacuolated egg, two smaller synergids-one of which usually disintegrates before fertilization-two polar nuclei of equal size, and three antipodal cells which may or may not persist. 6. The haploid number of chromosomes in A. cernuum is eight.

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