Included here is a large part of Sakhalin Island (south of 51 degrees 30 minutes), a large part of Hokkaido including the area northeast of the Kuromatsunai Depression, and the southern Kuril Islands including Kunashir, Shikotan and Iturup.
Of the endemic and near endemic vascular plants so far recorded there are about 210 species in 111 genera and 44 families. There is 1 endemic genus (marked red) but no endemic families.
Kanai, H. 1963. Phytogeographical observations on the Japano-Himalayan Elements. Journal of the Faculty of Science, University of Tokyo, Sect 3. Botany, 8: 305-339.
Numata, M. (ed). 1974. The flora and vegetation of Japan. Elsevier Scientific Publishing Company.