A begonia flower is monoecious, meaning it contains both male (staminate) and female (pistillate) parts. Flowers from begonias belong to a class of plants called angiosperms. It's in the flower of a plant where sexual reproduction in angiosperms takes place. Because angiosperms have reduced male parts and fewer female parts, it takes less time between the process of pollination and fertilization.
The stamen, which forms the male reproductive unit, consists of the anther and the filament. Usually the anther has two lobes. The anther is where pollen grains are produced. Pollen is a coarse powder that contains the microgametophytes of seed plants. These microgametophytes produce the male sperm cells known as gametes.
When an anther is young, it consists of a build-up of undifferentiated, thin, walled cells enclosed by an epidermis. As the anther matures, it develops into four lobes with the lobes joined by a sterile tissue called the connective. Within each lobe is an elongated chamber known as a pollen sac.
The female reproductive unit, known as the pistil, consists of three basic parts. The basal swollen part is called the ovary. The style is the cylindrical, narrow extension of the pistil. At the tip of the style is the stigma, which is a terminal receptive disc. The ovule starts developing as a tiny swelling on the placenta, forming a thick cell mass called the nucellus. As growth and development continues, the nucellus is elevated on the funiculus, which is a short, stalk-like structure. As the ovules further develop, protective layers grow from the the base of the nucellus called chalaza, which surrounds the nucellus (except for the narrow opening, called the micropyle). This opening is used as an entryway for a pollen tube into the ovule.
Petals and Sepals
Petals are the bright-colored portion of a flower surrounding the stamen and pistil. Considered the showpiece of a flower, petals attract not only humans, but also insects and birds. Sepals, which are usually green, typically lie below the petals and are leaf-like. Sepals serve as a temporary protective cover for an unopened flower. When a flower's petals are ready to unfold, sepals will fold back. According to the website Science.Jrank.org, wildflower begonias--which are not related to cultivated begonias--lack petals. Although wildflower begonias don't have petals, their colorful sepals look like petals. What's more, plant breeding of begonias has produced numerous showy flower begonia varieties.