The macrospore divides into two cells, a large lower one, and a smaller upper one. |
The nucellus is a cellular tissue enveloping one large cell, the embryo-sac or macrospore. |
But the formation of the macrospore or embryo-sac is simpler than the corresponding process in cryptogams. |
Fertilization in advanced plants is preceded by pollination, during which pollen is transferred to, and establishes contact with, the female gamete or macrospore. |