The distribution of rhein-type and aloe-emodin type anthraquinone glycosides in developing Cassia senna L. plants has been studied. The seeds contain no anthraquinones but shortly after germination chrysophanol, then aloe-emodin and finally rhein are formed in the young plant. In the presence of adequate light, glycosylation follows and significant quantities of glycosides appear in the young leaves. These are probably translocated to the flowers and ovaries since large concentrations of glycosides accumulate there. During fruit development the amount of aloe-emodin glycoside in the pericarp falls when the seeds become separable from the pericarp and the amount of rhein glycoside falls markedly when the seeds mature and become viable. It is suggested that in this plant anthraquinone production is intimately associated with fruit and seed development.