Experiments with bean seedlings were made to explain the fact that plants grown at low light intensities which show a delay in plant weight reach the same relative growth rates (RGR) as controls at high light level. The experiments confirmed the conclusion of Evans & Hughes (1961) that the constancy of RGR along a rather broad light intensity range can be explained by morphogenetic effects resulting in large differences in leaf area ratio (EAR). The delay in plant weight at lower light levels appears to arise in the early seedling stage when the morphogenetic adaptations are not yet accomplished.