The thermal algae which grew in the thermal water of Misasa Hot Springs, namely Mastigocladus laminosus Cohn (1), Phormidium ambiguum Gomont (2), Oscillatoria Cortiana (Menegh.) Gomont (3) and the fresh water alga which grew in the River Misasa, namely Rhizocolonium hieroglyphicum (4) were collected. The spectrographic analysis and quantitative chemical analanalysis of the ashes of the algae gave the following results : 1. All four algae contained Cu, Zn, Al, Pb, Mn, Mo besides the phisiological elements. 2. Two algae, (1) and (2) which grew in thermal water rarely mixed with the river water, contained Ti and considerable amount of Ge. 3. The highest content of Si and highest value of ash per cent were those of (1), and their values were 27.22 % and 26.44 %. 4. The highest content of Fe and Mn were those of (2), and their values were 17.80 %
and 3.27 %. 5. Great difference was not detected between the ratios of MgO/CaO of (1) and (2), and their values were 0.13 (1) and 0.14 (2).