EN
The cytological differentiation of the anthers’ tapetum in the tetraploid cytotype of Ranunculus fluitans Lam. (2n = 32) in relation to that in diploid cytotype of this species (Turała-Szybowska 1984) was studied. In the tetraploid plants the first acytokinetic mitosis is obligatory and leads to the formation of binucleate tapetal cells. Two further mitotic divisions do not comprise all cells. Contrary to the diploid cytotype, in the tetraploid these two mitoses most frequently, are not inhibited at prophase but may proceed further. The mitotic disturbances in the tapetal cells, like the bridges between two chromosome groups and the fusion of metaphase or anaphase plates result in the formation of a number of polyploid nuclei of irregular shapes. In the final stage, in different binucleate tapetal cells the nuclei evaluated as diploid, tetraploid or octoploid occur.