ABSTRACT
To assess the significance of a phenomenon one should know not only its structural background but also its frequency of occurrence. Our list of species with adventive embryony has been compiled from both published and original data. The taxa are in accordance with the system of Takhtajan. Nucellar and integumentary embryony most frequently are met in the families Rutaceae, Orchidaceae, Malpighiaceae, Poaceae, Rosaceae, Myrtaceae, Cactaceae, and Celastraceae. In Rutaceae nucellar embryony occurs in many species from the genera Aegle, Citrus, Clausena, Esenbeskia, Feronia, Fortunella, Myrraya, Poncirus, Ptelea, Triphasia, and Zanthoxylum. Seeds with nucellar embryo are more numerous than those of zygotic origin. Therefore, seed production is achieved by two mutually supplementary processes: amphimixis and nucellar embryony. The occurrence of adventive embryony and peculiarities of embryology in very few families prevent one from making some general statements. It seems probable that adventive embryony occurs in genera of various specialization levels.
