The chromosome numbers of the five species (Hosta rectifolia, H. opipara, H. venusta, H. amanuma and H. capitata) were 2n=60. The karyotypes of the four species (H. rectifolia, H. opipara, H. venusta and H. capitata) were as follows: the 60 chromosomes were in 30 pairs, which could be classified into four pairs of large chromosomes, two pairs of medium ones, and 24 pairs of small ones. The karyotypes of H. rectifolia varied according to the localities of the plants obtained, such difference being found mainly in the four pairs of large chromosomes. When large chromosomes change in form, they seem to follow three steps: 1) from chromosomes with subterminal primary constriction into ones with terminal constriction owing to the shortening of the short arm; 2) from chromosomes with terminal primary constriction into satellite chromosomes; 3) from satellite chromosomes into chromosomes with median or submedian primary constriction. The karyotype of H. capitata of the clone from Mt. Hakuunzan was the “original” one, while, that of Mt. Taradake presumably derives from the original karyotype. H. amanuma is verified to be the hybrid between H. capitata and H. venusta.