Okinoshima is a small island lying off the coast of the southwestern extremity of Shikoku. The island is about 20km in circumference and mainly consists of granite. The highest peak is Mt. Imose rising 404.1m above sea-level. The average annual temperature is 17.1℃, and the annual rain fall amounts to 1846.9mm. Herein is reported an outline of a vegetational survey of this island as compared with that of the southwestern part of the mainland of Shikoku. In Okinoshima the climatic climax forests are scarcely found owing to human activities. There-fore one is obliged to observe the residual fragments of them or the secondary forests. From this survey it is considered that Rapanaeto-Shiietum occupies the greater part of the island and Rumohreto-Machiletum occurs in rather limitted areas. These two associations belong to Rubel's laurisilvae. As typical climax forest of Rapanaeto-Shiietum is not found in this island, Rumohreto-Machiletum is observed as the only residual climatic climax which develops in low altitudes. In this island, Shiia sieboldii is frequently found in the areas of Machiletum and is often dominant in the tree layer. The main sociations of this Machiletum are Machilus thunbergii-Bladhia sieboldii-Alpinia chinensis sociation and Elaeocarpus elliptica-Bladhia sieboldii-Alpinia chinensis sociation. They show rather different structure compared with the same association found at Ashizuri-zaki and Muroto-zaki on the mainland of Shikoku. It seems that this association can be divided into two subassociations, namely, Bladhietosum (Okinoshima) and Podocarpetosum (Ashizuri and Muroto-zaki). Besides the above-mentioned climatic climax forests, the community chiefly dominated by stunted evergeen Quercus phylliraeoides occurs as an topographic climax on rocky places facing the sea. It is perceived that such garigue type communities which are commonly found throughout the coastal districts of Shikoku as well as Okinoshima should be included in the same association.
