Abstract
1. Diurnal Change of O2 produced by Diatoms: As far as the present investigation was concerned, O2-production due to the photosynthetic reaction by Melosira italica and Synedra pulchella of 106 individuals per litre was about 0.36c.c. in a day when the amount of solar radiation was calculated between 500 to 600 gr. cal., cm-2. The diurnal variation of O2 at the indoor place avoiding the direct sunlight was not recognized in the daytime, while in the dark O2 decreased about 0.2c.c. per litre.
2. Diurnal Change of O2 produced by Potamogeton crispus:- The O2-production due to Polamogeton crispus of 102 area of its leaf increased proportinally to the amount of the solar radiation for the corresponding unit time till the solar radiation rose to about 60 gr. cal., cm-2. and when the solar radiation became too striking (above 70 gr. cal.) the photosynthetic reactiog was weakened and O2-production decreased at the surface layer but in the 20cm. layer the grade of the harmful effect of the too strong solar radiation was weakened more or less.
3. When it was much cloudy or rainy the O2-increase was scarcely recognized.
