Abstract:The ultrastructural research of cell dedifferentiation in callus of safflower (Carthamus tinctorius L. ) revealed that active cell metablism occured when the cell dedifferentiation took place and stored lipid was used up during the early period of induction. Accompanied the dedifferentiation of vacuolate cells, the chloroplasts also went through a process of dedifferentiation. Their lamellar membrane swelled and degenerated. Meanwhile, the chloroplasts divided or budded anc1 finally became proplastids. The transfer of callus into the differentiation medium resulted in the redifferentiation of chloroplasts. The vesicles between cell wall and plasmalemma which were called paramural body were observed when the cell dedifferentiation and callus formation. The probable function of paramural body and the cause of chloroplast dedifferentiation have been discussed.