1. In the seeds of Datura tatula and Lupinus, the content of embryo factor increases with the development of the seed. A rapid growth of the embryo occurs two or three days after a rapid increase of the factor. 2. The highest content of the factor is observed at the time of the most active growth of the embryo. 3. In the older seeds the content of the factor decreases, but in the fully mature Lupinus seed a considerable amount of it is found. 4. The embryo factor is found also in placenta and fruit coat of Datura and in pod of Lupinus. The authors are indebted to Prof. S. Imamura, Kyoto University, for his guidance and counsel during the course of this study
