Abstract
The size change from wet fruits to carbonized cotyledons was investigated to compare the size of fossil fruits of Castanea crenata in different conditions from various Jomon sites. Both in height and width the size change from wet fruits to carbonized cotyledons had a linear regression. To critically compare fossil fruit size, a volume index for Castanea crenata fruits was calculated as the square root of height multiplied by width, because the cubic root of weight and the volume index showed a linear regression. The volume index of Castanea crenata fruits slightly increased during the early to late Jomon periods with narrow variation within populations, but varied greatly both between and within populaiton in the final Jomon period.
