In article ,
Stewart Robert Hinsley wrote:

In the majority of flowering plants the embryo sac (female gametophyte)
ends up with 7 cells contained 8 haploid nuclei. The pollen grain (male
gametophyte) has 3 haploid cells - the vegetative cell, and two sperm
cells. When the pollen grain germinates the vegetative cell grows down
the style to reach the embryo sac, carrying the two sperm cells.

One sperm cell unites with one cell from the embryo sac. The resulting
diploid cell develops into the embryo. The other sperm cell unites with
the embryo sac cell with the extra nuclei. This develops into a triploid
tissue - the endosperm - which is many plants provides nourishment for
the embryo after seed germination. (In many other plants the endosperm
is vestigial. There might be complications about syncytia as well - I
don't recall.)

Then I definitely misunderstood! You haven't come across a coherent
description of this, anywhere, have you? I mean in more detail.

All of the textbooks I have found are at a considerable more basic
level - that looks horribly like details not normally taught to
undergraduates.


Regards,
Nick Maclaren.