Megagametofyytin
Megagametofyytin is a term that does not appear routinely in standard botanical references and may represent a misspelling or variant of megagametophyte. When encountered, it is generally connected to the female gametophytic phase of seed plants, the haploid generation that develops within the ovule.
In seed plants, the female gametophyte, commonly called the megagametophyte, arises from a megaspore after meiosis.
In angiosperms, the megagametophyte is highly reduced and typically comprises an embryo sac with seven cells
The term megagametophyte (and by extension, megagametofyytin if used as a variant) represents the haploid component