Interestingly, regeneration was observed in all treatments including the control, which was devoid of any growth regulator ( Fig. 1). The supplementation of the culture medium with increasing concentrations of TDZ significantly increased regeneration to about 95 regenerants per leaf explant induced with 10 μM TDZ ( Fig. 1). However, the overall growth of the regenerants from leaf explants was better on 5 μM than on the higher TDZ levels. Even though some of the regeneration stages resembled those of somatic embryogenesis, simultaneous occurrence of shoot organogenesis was also observed in P. dryas cultures. It was difficult to precisely determine the ratio of embryo-like and shoot-like structures due to a very large number of regenerants developing in tight clusters. Both of these structures were able to form complete plants and therefore they are referred to as regenerants.