SUMMARYIn long root cuttings of Taraxacum, the regeneration of shoots was promoted by kinetin and the regeneration of roots by IAA, each hormone reversing the normal polarity of regeneration when applied at high concentrations. However, IAA stimulated shoot regeneration and kinetin root regeneration when used at low concentrations. A callus culture, derived from Taraxacum root, required both auxin and cytokinin for growth. At a given level of cytokinin, callus regenerated shoots when the auxin level was low and roots when it was high. A cytokinin from Taraxacum roots promoted callus growth and shoot regeneration in both callus and short root cuttings. Gibberellic acid had no stimulatory effect on organogenesis in either root cuttings or callus cultures.