A study was made of the endosperm-embryo relationship in the developing seed of T. officinale, a fully fertile, autonomous apomict. A related sexual sp., T. koksaghyz, served as the control. Seed development in T. kok-saghyz follows the pattern characteristic of the angiosperms. Endosperm and embryo development are initiated by double fertilization, and the 2 tissues are closely correlated in their subsequent growth. The endosperm is less precocious, however, than in most flowering plants. The mature ovule is low in food reserves. The T. officinale ovule stores a large mass of protein-rich nutrient material in the integument. Endosperm and embryo begin development without fertilization and apparently quite independently of each other. During the ensuing growth there is extreme diversity in the size ratios of the 2 tissues from seed to seed in the same head. For example, the embryo may attain a relatively advanced and normal development, while the endosperm remains one-celled. Conversely, the endosperm may become multicel-lular prior to division of the egg. Explanation of the fact that in the apomict embryo development may proceed normally in spite of even very limited endosperm growth probably lies in the extensive prestorage of food materials in the T. officinale ovule. The basic nutritive function which the endosperm performs in most flowering plants is thus rendered superfluous in this case.