Blastema

noun

1. A mass of undifferentiated cells from which an organ or a body part develops, either in normal development or in the regeneration of a lost body part.
2. A structureless substance from which it was formerly believed that cells are formed.
3. In bot.: Originally, the axis of an embryo, consisting of the radicle and the growing-point at its summit.
4. In later use, the initial point of growth from which any organ or part of an organ is developed.
5. Sometimes, the thallus of cryptogamous plants.