In 1908, E. F. Simon was able to induce callus from poplar stems that also produced roots and buds.[22] The first reports of callus induction in vitro came from three independent researchers in 1939.[23] P. White induced callus derived from tumor-developing procambial tissues of hybrid Nicotiana glauca that did not require hormone supplementation.[3] Gautheret and Nobecourt were able to maintain callus cultures of carrot using auxin hormone additions.[citation needed]