Meiosis produces four Megaspores in each Megasporangium.
Each Megaspore
is a Large Cell inside a thick, multi-layered wall.
The Megaspore cell contains
a lot of Storage Lipids.
It has a Triradiate Ridge which has three crests or peaks.
Cell
Divisions start beneath the crests & nowhere else. These lead to the
formation of a relatively thin cellular pad that lies on top of the storage lipids. Only a small fraction of the Megaspore becomes cellular.
Archegonia differentiate in the cellular pad, just beneath the crests of the Spore Wall.
This reminds me of embryo development in
chicks. The embryo starts out as a small disk of cells that floats on the lipid-rich yolk. |
Whole Megaspore:Note the Triradiate Ridge
Sections through a megagametophyte
Archegonia formed in the cellular region of the Megagametophyte
Megagametophyte with Archegonia
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