Two pollen grains of a Begonia flower. Begonia is one of the ten largest angiosperm genera. Terrestrial species in the wild are commonly upright-stemmed, rhizomatous, or tuberous. The plants are monoecious, with unisexual male and female flowers occurring separately on the same plant, the male containing numerous stamens, the female having a large inferior ovary and two to four branched or twisted stigmas. Most species come from tropical regions and therefore they and their hybrids require warm temperatures. Enhanced SEM. Image width: 53.6 micrometers. Magnification: 1,865x when image is printed 10 cm wide.