SummaryThe stigma and style are the sites where self‐incompatibility and hybrid sterility reactions occur in the sweet potato. The stigma is a highly branched structure covered with a specialized papillate epidermis which exudes a sticky fluid. The cells of the body of the stigma are arranged in gradually narrowing columns which conduct the pollen tubes from stigma to style. The style contains a central, uniform core of pollen‐tube conducting tissue. The junction of style and ovary provides a continuous but contorted pathway of conducting tissue which pollen tubes follow. The incompatibility reaction, which occurs at the stigmatic surface, is hypothesized to be due to interactions of substances in the pollen and in the stigmatic exudate. Sterility, on the other hand, may be due to pollen tube disorientation or failure at the stigma‐style junction and the style‐ovary junction, where passage may be mechanically more difficult.