Abstract
Between water temperature and the crop of Undaria pinnatifida (HARV.) SUR in the province of Hukuyama, western Hokkaido, the correlation coefficients were found to be as high, as r=0•68 in August, the season for the zoospores to be discharged, and as r=0•69 in June, when the alga is liable to be washed away if temperature is too high. The results are in agreement with those found in northern Hokkaidô by KINOSITA and SIBATA, and also in Etizen by KAWANA, though in the latter district (Etizen), the crop season of this alga is a month earlier than in Hukuyama.
