Spontaneous infections seem to indicate that not only the crown of herbeous plants is disposed to generate tumors. Under substrate conditions such as those normally found at the crown, infections caused by Agrobacterium tumefaciens will yield tumors in the entire area of the roots.Roots of Helianthus annuus and Solanum lycopersicum grown in nutritive medium are disposed to tumor when given appropriate conditions of culture and inoculation. Tissue culture, the most widely applied method for the analysis of bacterial plant tumor, has a disadvantage in the correlation with the whole organism is lacking. This disadvantage is avoided when submerse cultures on intact roots are used, and the methodical advantages involved in using tissue cultures are preserved.When two unfavorable factors such as lack of oxygen and suboptimal temperature come together, a slowing down of tumoral induction results in hydroponic culture. Tumors already induced will grow normally. When the induction temperature is optimal (for Helianthus annuus 26°C) lack of oxygen will not produce inhibition of induction. Lack of oxygen will, however, unfavorably effect the total development of the roots in any case.Proportional dependence between the growth of the roots and that of the tumor does not exist. Tumors of medium size correspond to a maximal weight of roots. This paper discusses the relationship between the above mentioned phenomena and growth hormones.In the tests involving lack of oxygen epinasty could be observed.