[Apomixis and amphimixis in flowering plants].

The light microscopic and ultrastuctural events of apomictic seed development from the earliest stages through the embryo and endosperm development to maturity were compared with those of the sexual one. The problem of autonomous endosperm formation was postulated as the main problem in low apomictic seed set. The characteristic features of fine differentiation of megasporocytes at diplospory, aposporous initials at apospory, embryocytes at adventive embryony as well as the egg cells at parthenogenesis and synergids at apogamety were described and compared with sexual reproductive structures. It was supposed that the observed similarities in differentiation at the cell level are the result of identical mechanisms of genetic regulation of reproductive structures at amphimixis and apomixis.