The taxonomic studies of the genus Inocybe

136 taxa of Inocybe (Cortinariaceae, Agaricales) are identified and described. Nine new taxa and a new combination are proposed based on materials collected from Japan and America. Thirty-four records of Inocybe are new to Japanese mycoflora. The present study proposes a new infrageneric system of the genus Inocybe. Two new subgenera are established based on cystidia-character and spore-character. In the unique combination of the characers of cystidia and spores, Inocybe leptocystis and Inocybe conicoalba has thin-walled pleurocystidia and smooth spores. Two Inocybe belong to new subgenus Tenuicystidia T. Kobayashi. While, a new species of Inocybe, Inocybe leptoderma T. Kobayashi & Nukada has thin-walled pleurocystidia but spores are angular. Worldwide, the author has observed this type of Inocybe, namely Inocybe tahquamenonensis from USA, Inocybe magnifica from Papua New Guinea, Inocybe parcecoacta from USA and Inocybe leptophylla from USA. They belong to a new subgenus Pertenuis T. Kobayashi. All previously reported taxa of the genus Inocybe in Japan are treated in this work. Hongo and Kobayasi described several new Inocybe from Japan. The author examined their type specimens or fresh collections.