The Puriri is self-fertile with self-fertilization (autogamy) possible. Without the rejuvenating effects of autogamy or conjugation a "Paramecium" ages and dies. Self-pollination is an example of autogamy that occurs in flowering plants. The term xenogamy (along with geitonogamy and autogamy) was first suggested by Kerner in 1876. "Paramecium aurelia" is the most commonly studied protozoan for autogamy. Conjugation and autogamy are always followed by fission. The hermaphroditic flowers are either self-fertilized (autogamy) or pollinated by insects (entomogamy). If this occurs in an individual it is recognized as autogamy. This is often the product of autogamy, in which case the cysts produced are zygotes. Self-fertilization (selfing, or autogamy) is more common in annual compared to perennial herbs. In flowering plants, it is believed that autogamy evolved one million years ago. Actinophryids also undergo autogamy during times of food scarcity. This structure involves an efficient autogamy mechanism, that guarantees the self-fetilization. Autogamy has been observed in several species of onion orchid. However, species of protists have also been observed using autogamy as a means of reproduction.