Abstract
In a clone of Hosta undulata Bailey (2n=60, Text-fig. 1) extremely aberrant meiosis was observed. All PMCs observed showed abnormal configurations especially of larger chromosomes at diakinesis and MI, such as, univalents (Text-figs. 4-19), fragments (Text-figs. 7-19), translocated segments (Text-figs. 10-13), terminally associated bivalents (Text-figs. 7, 8 and 16) and polyvalents (Text-figs. 12-14), the last being interpreted as the results of reciprocal translocation. These abnormalities lead to the aberrations of chromosome behaviour in the farther stages, such as, occurrence of lagging chromosomes, fragments, chromatin bridges etc. (Text-figs. 20-26). These aberrant karyokineses, however, arc followed by normal cytokineses, no microcyte being formed at the tetrad stage. The pollen grains are almost completely sterile and no seed is produced. These abnormal chromosome configurations observed are ascribed to certain structural changes occurred at the early stage of meiotic prophase, which are supposed to be genetically controlled. The author is indebted to Professor H. Matsuura under whose guidance and criticism this work has been carried on.
