In flowering plants, the female megaspore mother cell divides to produce several cells, one of which is the egg cell. Each pollen grain contains 4 microspores. Eventually, one sperm combines with the egg to produce a diploid zygote, which will divide mitotically to produce the sporophyte. Another sperm will fuse with other haploid nuclei of the female gametophyte to form a 3n or 5n nucleus. This tissue becomes the endosperm, which is utilized by the developing sporophyte.
Flowers are modified leaves.
These may resemble the showy petals, but often are small, green structures. Collectively, the sepals are called the calyx . Petals are the showy portion that we usually think of as the flower. Petals act to attract pollinators to the plant. Collectively, the petals are called the corolla.