Tumori na listu graha inducirani bakterijom Agrobacterium tume- faciens (I 1-4 i B6)

Agrobacterium tumefaciens, strains B6 and I1-4 and crown-gall tumors, which they induced on bean leaves, were investigated by means of light and electron microscopy. The results show: 1) When the bacteria of the strain I1-4 are reisolated from primary tumors their colonies show the S-forms as a rule. The view, that at low temperatures the R-form changes to the S-form, cannot be confirmed. 2) In the cells of both strains of Agrobacterium tumefaciens it has never been possible to prove any signs of the presence of a bacteriophage. 3) In living tumor cells the only cell organelles, which showed considerable ultrastructural changes, were the plastids. In other cell organelles no ultrastructural changes could be stated with certainty.