Both sexes practice scarification and circumcision/female genital mutilation. Tremain also argues that some types of tattooing and scarification symbolized valor and bravery. Chemical scarification uses corrosive chemicals to remove skin and induce scarring. In some seeds physiological dormancy is indicated when scarification increases germination. Seed germination may be aided by scarification. Propagation of ceanothus is by seed, following scarification and stratification. These vaccines may be given by aerosol, scarification, or subcutaneous injection. Human branding is one type of scarification. There are also aesthetic, religious, and social reasons for scarification. The pattern of Nuer scarification varies within specific subgroups. Some forms of their art include body scarification. A traditional form of visual art is body scarification. The relationship between scarification of body parts and pathogen prevalence was not evident for males. The process is known as scarification. The most common type of scarification is mechanical scarification.