Abstract
Summarizing princhipal res lts obtained by our present investigation, we are inclined to think that life-history of Porphyra yezoensis follows a course described below.
Carpospores discharged in spring germinate directly after the discharge. Hence, in summer we usually find them, because of inadequate conditions of environments, remaining as minute fronds throughout the season. However, when external conditions are favourable, they assume the normal course of development even in summer.
These “summer plantlets” initiate an active discharge of monospores as temperature of sea-water approaches to ca. 20°C., and from the monospores thus dischrged develop autumn buds.
The summer plantlets grow on with lowering of water tempetature, discharging continually monospores. The autumn buds too, attaining form of minute fronds, discharge monospores, but this activity is limited in a range of water tamperatures between 20°C. and 15°C.; formation of the monospores is seriously affected by temperatures below 15°C. Consequently, the duration of discharge of the monospores covers a considerably extended period of the year (from September to October at the Bay Usu), and the monospores of delaye I production are considered to develop to December buds and to early winter buds.
With fall of water temperature the formation of the monospores comes to an end, a chief occurrence under such condition being growth of the fronds, which includes formation of male and female sexual cells at the peripheral portions. The carpospores then formed germinate directly after being discharged, and from this fact we consider that these carpospres will further develop to most of the winter buds and to the apring buds.
