 "Silene" species commonly contain a mixture of hermaphroditic and female (or male-sterile) individuals (gynodioecy), and early studies by Correns showed that male sterility could be maternally inherited, an example of what is now known as cytoplasmic male sterility.Two independent groups of species in "Silene" have evolved separate male and female sexes (dioecy) with chromosomal sex determination that is analogous to the system found in humans and other mammals.