Abstract
In the previous paper the author reported that Edgeworthia papyrifera was allotetraploid and its two races. Shizuoka and K6chi, were of different genome constitution. He also reported the artificial induction of an octaploid of Shizuoka race by means of colchicine Itreatment. This octaploid plant proved to be self-incompatible like the original tetraploid. giving no seed on selfing. Crosses between the octaploid and the tetraploid Shizuoka race were successful only when the former was taken as the fenale parent, the resulting offsprings of which were confirmed to show the hexaploid number of chromosomes (2n = 54) in their root tip cell division. Abundant hexaploid offsprings were also obtained from the shoots of the octaploid left for open pollination. It is thus' clear that, being self-incompatible, ovules of the single octaploid plant left under natural conditions have no choice but to be fertilized by pollens of the tetraploid grown nearby. Microsporogenesis in the original tetraploid Shizuoka race was carried out quite normally, presenting 18 bivalents at MI. In the octaploid, more than half of the MI nuclear plates investigated displayed normal arrangement of 36II, but the remaining ones showed formation of 1-3 quadrivalents and rarely I trivalent. The division was, however, observed to proceed fairly regularly, showing almost equal assortment of daughter chromosomes at AI. In the hexaploids the microsporogenesis went on considerably irregularly. There were always found trivalents and randomly scattered univalents at MI, the former ranging in number from 4 to 10 and the latter from 4 to 7. The commonest configuration was 6III+ 15II + 6 I . In most cases the univalents lagged and remained near the equatorial region at AI, resulting in the formation of tiny, supernumerary microcyte nuclei.
