In Japan, ancient-tertiary floristic elements survived during the Ice Age because the Japanese Archipelago lies from south to north and has no dry land. These elements are found mainly in the temperate zone. The mountains of Japan do not reach high alpine altitudes of the world. It is thought that the alpine floras of Japan are derived directly from the northern sub-boreal zone (Euro-Siberian region) during the last Ice Age. The evergreen conifer forest in the subalpine zone in Japan is composed mainly of Abies veitchii L1NDL., A. mariesii MAST. and other taxa that are endemic to Japan. This forest is thought to be a cold temperate forest belonging to the Sino-Japanese region. Laurel-leaved forest (warm temperate forest) occurs in the southern part of Japan, and extends northward to Tohoku district of Honshu. Dominant species in this forest are distributed from Japan to southern China but not beyond the Sino-Japanese region. Most species in this forest represent the northern extreme in distribution for genera that have many different species in the mountain region of South-east Asia, in contrast the alpine floras of Japan that range widely in the north area.
We describe wood fossil assemblages excavated from a wood peat bed (E bed) deposited 3500 to 3000 yBP, and a more recent herbaceous peat (B bed) deposited after 2000 yBP, in the southern part of the Mikata lowland along the Mikata fault. Vegetation in central to marginal areas of the lowland was reconstructed from species identifications based on stump, stem, stick, and root material. The E bed assemblage in the central lowland indicated a wetland forest composed mainly of Alnus subgen. Alnus and Fra.xinus. This forest declined for some reason at ca.3000 years ago. The B bed assemblage in the central lowland indicated a partly developed wetland forest with Alnus subgen. Alnus. The E and B bed assemblages in the marginal area of the lowland indicated the coexistence of the same wetland elements with conifers such as Cryptomeria japonica and Thuja standishii.
Forsythia, a genus with six species, is a deciduous tree and confined to temperate areas in Asia and Europe. Forsythia pollen have been only briefly characterized by light microscope (LM) observation (WODEHOUSE, 1935; ERDTMAN, 1952; etc.). Our present knowledge of pollen morphology among East Asian species of Forsythia is scant. Here we report LM and SEM observations of pollen from four species with one variety: F. suspensa (THUNB.) V AHL, F. japonica MAKINO, F. japonica var. subintegra HARA, F. viridissima LINDL., and F. koreana (REHDER) N AKAi. These species are distributed in Japan, Korea, and China.