This study, concerned with the nitrogenous constituents of the tissues of A. comosus (L.) Merr. grown in nutrient solutions containing either high or low amounts of potassium and supplied with equal quantities of nitrogen either as nitrate or ammonium, is intended to furnish information on potassium and nitrogen interrelationships in growth. Ash constituents, chlorophyllose pigments, titratable acidity, and carbohydrates in the same plants were reported in earlier publications (20, 21). The effects of nitrate and ammonium nutrition on the nitrogenous fractions of A. comosus were also reported previously (22), but without variation in potassium.