n. In bot.: Originally, the axis of an embryo, consisting of the radicle and the growing-point at its summit.n. In later use, the initial point of growth from which any organ or part of an organ is developed.n. Sometimes, the thallus of cryptogamous plants.n. In anatomy and physical, the bioplasm or protoplasm of a germinating ovum; the substance of the blastomeres, blastoderm, etc.; granular formative material.