In the previous paper, the authors reported that flavoviolet (1-ribityl-2-oxo-3-hydroxy-6,7-dimethylquinoxaline) was found in the leaves, when the above-ground part of a pea plant was water-cultured in riboflavin solution. In this paper, the authors reported that this substance was found not only in the riboflavin-cultured pea plant, but also in some of the natural plants. When the above-ground part of a pea plant was water-cultured in the flavoviolet solution, the amount of riboflavin increased. The higher the concentration of flavoviolet was, and the more the cultured days went on, the higher the rate of riboflavin increase became. Then there appeared a new blue fluorescent substance having the Rf value of 0.26 (butanol・acetic acid・water=4 : 1 : 5). In this case, this substance may be assumed as an intermediate in riboflavin formed from flavoviolet.