As one of the algal habitats, the soil surface has fairly complicated components of algal vegetation in spite of their restricted ecological fcctors relating to the moisture condition. On the other hand, the characterized algal vegetation can be observed as a result of an adaptation to an aerial condition. It has been stated by G.S.West and F.E.Fritsch that an inconceivable number of algae are able to thrive on terrestrial and subterraneous conditions. In 1931, J.B.Petersen presented an account of the ecological study of algal vegetation of Hammer Bakker, and had recorded a number of Cyanophyceae, Diatoms, Xanthophyceae and Chlorophyceae, in addition, four species and one forma of Chlorophyceae were newly described.
In 1935, an excellent historical summary of the study of soil algae was given by J. B. Petersen. In this summary, through such studies as Graebner on the heaths of Germany, Warming on the biology of marshes, Fritsch on the terrestrial algae of the tropics, and the cornments of Treub on Cyanophytan immigrants to Krakatoa he represents some of the earlier attempts at analyzing the algal vegetation of various habitats.
In 1932, an extremely aerobic alga Fritschiella tuberosa Iyengar was discovered by M.O.P. Iyengar from India. Later, the life history and the autoecology of this alga were studied by R.N. Singh (1941), and still later, J. Brook (1953, 1956) reported that the alga grew in Sudan of Egypt and had many peculiarities as a terrestrial alga.
Recently on the micro-flora of subterraneous algae, F. R. Trainor and H. Bold (1953) reported three new unicellular Chlorophyceae viz. Hormotilopsis, Chlorococcum and Characium from soil. Later, W. Herndon (1958) isolated certain new species of Chlorosphaeracean and Chlorococcacean algae from the soil of Jamaica, and G. Arce and H. Bold (1958) isolated certain new species of Chlorophyceae from Guban soils.
On ecological study of soil algal flora, L. M. Shields, C. Mitchell and F. Drouet (1957) investigated from the view that alga-and lichen-stabilized surface crusts would be soil nitrogen sources.
In 1926, H. Molisch made the first botanical report on epiphyllous algae in Japan. Now, S. Suematu has been studying on parasitic and epiphytic aerial algae such members as Trentepohlia, Cephaleulos and Phycopeltis in Japan, and several reports on those algae have been published. Recently, H. Hirose and the present author have newly collected a terrestrial alga Fritschiella tuberosa Iyengar from Japan. Later, an account of new records of several terrestrial and aerial algae from Japan has been given by the present author.
In this paper, the author wishes to report the preliminary survey dealing with an ecology of aerial and terrestrial algae in San'in region of Honshu, Japan.