Meiotic behaviour of two X-ray induced mutants of Pisuin sativum showing reduction of number of chiasmata was analysed. As a consequence of presence of many univalents in the pollen mother cells manifold irregularities appeared during the later stages of meiosis causing a high proportion of non-functionable germ cells. Corresponding abnormalities are realized in macrosporogenesis resulting in a high reduction of fertility.
Clear differences between both of the mutants were observed in several subsequent generations in respect of the degree of meiotic irregularities and seed production evidencing that the mutants are not identical. It could not be clarified so far whether two different genes or two alleles of a multiple series have changed.