| Both types of cleistogamous flowers are fertile and undergo self-fertilization. |
| Physid snails usually cross-fertilize but are capable of occasional self-fertilization. |
| Because self-incompatibility operates after pollination, it reduces geitonogamous self-fertilization but not geitonogamous pollination. |
| Gametophytic self-incompatibility is a widespread mechanism in flowering plants that prevents self-fertilization and promotes out-crossing. |
| Thus the stigmas of flowers are able to identify the genotype of pollen and avoid close inbreeding and self-fertilization. |
| Chemical self-incompatibility is another device for preventing self-fertilization. |
