To obtain the maximal production of pollen embryoids in cultured anthers of Datura innoxia, the critical stage of anther development and the effect of physical factors, such as the precise mode of implantation of the anthers in the culture medium, light, temperature, and pH, were studied. In almost all media used, anthers containing uninucleate pollen were the best for initiation of embryogenesis. Variations in light and temperature also affected development of the embryoids significantly. The percentage of anthers producing pollen embryoids increased almost linearly when the temperature was raised from 22 to 30 °C. At lower temperatures (15 to 20 °C) no embryoids were produced. Cultures kept in darkness produced embryoids, but upon transfer of cultures to the light the percentage of responding anthers increased considerably.