Archegonia are absent in the ovule of ...................... .
Gnetum
Archegonia are the flask-shaped female sex organs. Among gymnosperms they are retained in the female gametophyte of Cycas, Pinus, Taxus and most others, where each archegonium encloses an egg cell.
In Gnetum (and Welwitschia), the female gametophyte is highly reduced and does not form archegonia; instead, free nuclei in the micropylar part of the gametophyte act directly as eggs. This is one of the angiosperm-like features of Gnetales.
Cycas, Taxus and Pinus all bear distinct archegonia in their ovules.
Hence, the answer is Gnetum.
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