Abstract: Following a complete ringing of the main stem of Eucommia ulmoides Oliv. regeneration of normal new bark has been observed as a subsequence of repeated partial differentiation of the immature xylem into cambium. The immature xylem, when cultured in vitro, showed production of callus tissue from the ray cells. After 15–30 days of continuous culture, meristematic tissue appeared as a discontinuous and more or less regularly arranged.zone was visible within the callus tissue. However, the meristematic cells, unlike the elongated fusif0rm initial cells, are isometric in shape. This meristem differentiated into tracheids centripetally. Nevertheless, no centrifugal differentiation into phloem was evidenced. The vascular tissues were ultimately degenerated after 6 months cultured in vitro.