Maximum DNA synthesis during the midproliferative phase of the cycle (i.e. cycle days 8â10) correlates with the maximum number of mitoses in both the stromal and epithelial endometrial cellular elements, as well as with the midproliferative peak of plasma estradiol and nuclear estradiol receptors.
Some defining characteristics of angiosperms include flowers, carpels, and the presence of endosperm, a nutritive substance found in seeds, produced via a second fertilization event. However, some current studies suggest that endosperm is not unique to angiosperms.
In, 1898 the Russian cytologist S. G. Navashin discovered double fertilization in angiosperms, which consists in the union of a sperm-ucleus with an egg cell nucleus and the union of a second sperm nucleus with the nucleus of an endosperm-producing cell.