Q. How is the gymnosperm seeds formed? What are the ploidies of the structures that compose the seeds?
Their seeds are produced from differentiation of the megasporangia in the female strobiles (cones). Subsequent to an oosphere is fecundated the female gametophyte originates the haploid (n) primary endosperm (nutritive tissue that covers the embryo) and the covering of the megasporangium turns into the diploid (2n) seed shell.