A strain of tissue of common rue of root origin (index of the strain R-4) has been obtained which produces up to 3% (of the dry weight) of acridone alkaloids. It has been shown by physicochemical methods that the combined alkaloids consist mainly of 1-hydroxy-N-methylacridone, rutacridone, and 1-hydroxy-3-methoxy N-methylacridone (0.28, 0.81, and 2.41 mg/g dry weight of tissue, respectively). Strain R-4 is a good model for the study of little-known steps in the biogenesis of the acridone alkaloids. © 1985 Plenum Publishing Corporation.