Akan National Park, located in the north-eastern part of Hokkaido, have many thermal and hot springs or sulphur springs in the area. Any biological investigation of thermal inhabitants have hardly been carried out up to the present. The writer made an collection tour for the purpose of clearing their thermal vegetation in August 1938 and collected about 109 tubes of formalin preserved material. After careful examination he identified 34 species and varieties in all. Most of them belong to Cyanophycean algae, but diatoms and Chlorophyceae are small in number. Here the results are reported except those of Akan-ko-han (or Akan Lake-Side) Hot Springs, of which was previously informed in this Acta. The lists of algae of each hot spring are given below. I. Kawayu Hot Springs. The only algae which grow in this acid spring is Cyanidium caldarium (TILD) GEITLER. The plant occurred in hot water of temperature 38-65℃ and pH 1.2-2.6. II. Tesikaga Hot Springs. Cyanophyceae : (1) Gloeocapsa arenaria (HASS. ) RABENH. 30℃. (2) Synechocystis aquatilis SAUV. Diam. of cells 4-6μ. 30-40℃. (3) Synechococcus elongatus NAG. var. amphigranulatus COPELAND. 40-63℃. (4) Oscillatoria chalybea MERT. 40℃. (5) Phormidium tenue (MENEGH. )GOM. 40℃. III. Tobtu Hot Springs. Cyanoplyceae: (1) Chroococcus minutus (KUTZ. ) NAg. 41℃, pH 7.3. (2) Synechococcus elongatus NAg. 40-41.3℃, pH 7.3 (3) do. var. amphigranulatus COPELAND. 59.2℃, pH 7,3. (4) Oscillatoria terebriformis AG. 41-41.3℃, pH 7.3. (5) O. amphibia AG. 59.2℃, pH 7.3. (6) O. Cortiana MENEGH. 31.2-41.3℃, pH 7.0-7.3. (7) O. brevis KUTZ. 41℃, pH 7.3 (8) Phormidium angustissimum W. et G. S. WEST. 59.2℃, pH 7.3. (9) Ph. laminosum (AG. ) GOM. 40-41.3℃, pH7.3. (10) Lyngbya lutea (AG) GOM. 41℃, pH 7.3. Bacillariophyta: (11) Achnanthes exigua GRUN. 41.3℃, pH 7.3. (12) Navicula cryptocephala KUTZ. 41.3℃, pH 7.3

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