There have been many descriptions of the morphological expression of mutant genes in the mature plant body, but relatively little has been done on gene expression in early stages of ontogeny in higher plants. The fact that many genes have marked expression in older plants raises the question of the extent to which they are manifested at earlier stages of development. In the present study an embryonic structure of maize, the scutellum, is investigated for evidence of expression of a simple Mendelian recessive, dwarf-one (d1). Four different inbreds were used because it was anticipated that quantitative expression of the gene would be modified by association with different genotypes. The scutellum was chosen as the specific subject of study since preliminary investigations indicated that scutellum shape varied from one inbred to another. It seemed possible, then, that a single gene difference might also show some expression in this organ.