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Percentages of melilotic acid, o-coumaric acid, and coumarinic acid were highest in leaves, intermediate in stems. and lowest in roots of greenhouse-grown sweetclovcr plants of the CuCuBB genotype. In leaves, percentages of each of the three compounds decreased as the leaves grew older. but amounts per leaflet increased with age except for content of o-coumaric acid, in which a brief increase was followed by a sharp decrease. Seed from plants of the Cu phenotype was higher in content of each of the three compounds than seed from cu plants. Levels of o-coumaric and coumarinic acids were much lower in seed than in young leaves. First- and second-year field-grown plants of the CuCuBB, CuCubb, cucuBB, and cucubb genotypes were sampled at intervals throughout the 1961 growing season. Leaves, stems, and roots were assayed for melilotic acid, o-coumaric acid, and coumarinic acid. Melilotic acid content was lowest in each of the tissues assayed, and percentages of each of the three compounds were considerably higher in CuCu plants than in plants of the cucu genotype. The B/b alleles appeared to influence melilotic acid synthesis since CuCuBB plants contained significantly more melilotic acid than CuCubb plants. Levels of o-coumaric acid and coumarinic acid were not affected by the B/b alleles. Contents of the three compounds were found to vary considerably during the growing season.