Inside the peeled bark of Eucommia ulmoides Oliv. the immature secondary phloemwhich included ray cells and other living cells of the phloem, under cultures for vitro, coulddevelop callus from which it further differentiated discontinuously into meristematic zoneor formed some tracheids directly. Later on clusters of tracheid-like elements appeared.The callus coming from the phloem of male trees also differentiated into the primordia ofadventitious buds and roots. However, no sieve cell-like elements were developed in thephloem callus after culture in vitro. Inside the peeled bark of Eucommia ulmoides Oliv. The immature secondary phloemwhich included ray cells and other living cells of the phloem, under cultures for vitro, coulddevelop callus from which it further differentiated discontinuously into meristematic zoneor formed some tracheids directly. Later on clusters of tracheid However, no sieve cell-like elements were developed in the phloem callus after culture in vitro.