The inheritance of peltate glandular trichome (PGT) formation in PERILLA FRUTESCENS leaves was investigated by crossing a normal strain with a variant strain with sparse PGT formation. The F (1) and F (2) data suggested that the sparse trichome is a dominant character that is controlled by a major gene and a few modifying genes which specifically inhibit the development of trichomes of the peltate type. Tracer experiments using [ (14)C]-sucrose showed that the quantity of essential oil components synthesized in the leaf was positively correlated with the number of PGTs, suggesting that the PGT is the main site for the biosynthesis of essential oil.