Abstract
1) A great number of rice varieties were exa-mined in order to clear up how heading time and growth period before heading be changed by delayed seeding. 2) In general, the heading time becomes later in accordance with delayed seeding, but the growth period before heading is shortened. 3) Owing to the extents and types that the growth period before heading is shortened, many varieties were classified finto two groups which correspond to the two groups described in the previous repor, ts, e. g. the Ist group, which is more sensible to higher temperature and less to short day-length, and the 2 nd group, which is less sensitive to higher temperature and more to short day-length concerning ear emergence. 4) Because the heading time is determined by the length of the basic vegetative growth period. and also by the responsibility for temperature and, , dayilength, the relation of heading time between earlier variety and later one in usual cultivation is expected to be reversed sometimes when seeding is delayed so far. 5) On the geographical and local distribution of rice varieties it may be seen that in Japan, varieties belonging to Ist group are mainly cultivated in Hokuriku area and more northern parts, and varieties involved in 2rid group in Kanto area and more southern parts of Japan ; in China, there are two types of varieties, although they are not so clearly distinguished as the case in Japan ; and in South-East-Asia, only varieties of Ist group are dlstributed . 6) The results obtained in this experiment lead to the conclusion that the changes of heading time by delayed seeding and the distribution of varietiein all parts of the world should mainly be determined by the responsipility of rice for temperature and day-length
