Abstract
There are two varieties, Shizuoka and Kochi of Edgeworthia papyrifera in Japan. The are easily identified with their difference in certain characters. It is especially noted that the Kochi variety is highly sterile in self and free pollination. However F1 hybrid were easily obtained in reciprocal crosses between Kochi and Shizuoka varieties. From this fact it can be assumed that the high sterility of the Koch variety is due to (1) the self-sterility found generally in Edgeworthia, and (2) that its population originated by a vegetative propagation of or a few original plants. A comparative study was made with some morphological characters i n the hybrids and their parents (Tables 1-6). Meiotic pairing of chromosomes in PMC-s were also extensively observed in the hybrids and their parents. In each of them 18 bivalents were normally formed in most cases, but the formation of one to two quadlrivalents or the failure of chromosome pairing in a few bivalents were occasionally observed. All these data obtained so far suggest strongly that Kochi and Shizuoka varieties show nothing but genic differences found in just the usual varieties.
