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Hydroxylamine (HA), 2-aminopurine (AP), 5-bromouracil (BU), and ethyl methanesulfonate (EMS) were tested for mutagenic activity on seeds of Melilotus alba annua. Mutants were classified into the following categories: o-hydroxycinnamic acid (o-HCA) content and β-glucosidase activity, chlorophyll deficiency, dwarf growth habit, and miscellaneous morphological variations. Due to difficulties in classification, the o-HCA and β-glucosidase category and the dwarf category were unreliable for determining mutation rates. Based on the chlorophyll-deficient and miscellaneous morphological categories, mutation rates for HA, AP, and BU treatments did not differ from the control rates, but EMS at 0.003M and 0.004M concentrations was highly effective in inducing mutations in these. categories. Mutation rates based on chlorophyll deficiency were somewhat higher and more sensitive to EMS concentration than were mutation rates based on the miscellaneous category. Large numbers of chlorophyll, dwarf, and morphological variants, several more vigorous than the controls, were isolated from the EMS treatments, but no new o-HCA or β-glucosidase mutants were obtained.