Branch length distribution, frequency of formational change in lateral branches, and foliage mass distribution in individual branches were examined for Thujopusis dolabrata var. hondae saplings to examine the ecological causes of the formational change in branches. Formational changes were observed in 29% of all lateral branches studied, and were more frequent in branches ramified at lower height. Lateral branches showing formational change were characterized by their longer length and high C/F ratio compared with branches with no formational changes. Foliage mass on branches having formational change showed a skewed distribution and were concentrated in peripheral shoots extending from the outer crown of the formational change. We hypothesize that the formational change provided the sufficient foliage mass for the survival of saplings and lateral branches in extremely low light. Most of the observed layerings (95%) showed formational change. However, this tendency is probably to be attributable to the fact that branches with formational changes tend to be longer and ramify at lower heights than those with no formational changes.