Abstract
The paper presents anatomic structure of root nodules of lupine (Lupinus luteus L. cv. Express) and ultrastructure of cells infected by Rhizobium, The inside of cells from the infected nodule region was filled with numerous bacteria; only centrally located cell nucleus was free of bacteria. Rhizobium was present mostly in the form of "transforming bacteria" (according to the terminology by Ching et al. 1977), characterized by visible nucleoid areas, numerous ribosomes, and polyphosphate granules, although typical bacterioids with poly-β-hydroxybutyrate were also found.