embryo sac

noun

, Botany.

1. the megaspore of a seed-bearing plant, situated within the ovule, giving rise to the endosperm and forming the egg cell or nucleus from which the embryo plant develops after fertilization.

embryo sac

noun

1. the structure within a plant ovule that contains the egg cell: develops from the megaspore and contains the embryo plant and endosperm after fertilization

embryo sac

1. An oval structure within an ovule of an angiosperm that contains the egg. Together with the fertilized egg, it develops into a seed. The embryo sac is the female gametophyte of angiosperms, consisting of eight nuclei: the egg and two adjacent and short-lived synergids that are near the micropyle (the opening where the pollen nuclei will enter), two central nuclei (which will combine with one of the pollen nuclei to form the endosperm), and three antipodal nuclei at the end of the embryo sac opposite the micropyle. Like the synergids, these nuclei degenerate at or shortly after fertilization.
2. See more at gametophyte

Word History and Origins

Origin of embryo sac¹

First recorded in 1870–75

Example Sentences

And he observed the extension of the embryo-sacs up the style and the union of the pollen tube with the tip of the embryo-sac.

From Project Gutenberg

He also recognised and figured the great prolongation backwards of the embryo-sac as an empty, absorbent caecum.

From Project Gutenberg

There he continued his study of the embryo-sac in Orchideae, as Sachs subsequently testified, "zu meiner vollsten Zufriedenheit."

From Project Gutenberg

But the formation of the macrospore or embryo-sac is simpler than the corresponding process in cryptogams.

From Project Gutenberg

One of the cells of the nucleus near its apex then enlarges, so as to form a sac, called the embryo-sac.

From Project Gutenberg