1. Ovule: This is the female reproductive part of a flower. It contains the egg cell, which will eventually develop into the embryo of the plant.

2. Pollen: This is the male reproductive part of a flower. It contains sperm cells, which will fertilize the egg cell in the ovule.

When pollen from a flower reaches the ovule, the sperm cell fertilizes the egg cell. This fertilized egg then develops into the embryo, which is enclosed within the seed.