“…But at 0.056 to 0.56 ppnm iron supply low manganese depressed peroxidase and at 0.056 to 1.4 ppm iron supply excess manganese increased peroxi(lase, the increase being very marked and statistically significant (fig 13). In leaves other than the first, at the normal manganese supply, peroxidase was dlepressed within the range 0.056 to 0.56 ppm iron supply and, but for one exception, not affected within the range 1.4 to 28 ppm iron supply (fig 14, 15, 16 (8) Lespedeza (24) and certain other plants (41) but not in soybeans (37) oats and tomlato (40) and sunflower (42) The yield of plants showed a significant interaction of iron and manganese supply. In contrast to the findings of Pugliese (34) for wheat, Scharrer and Schropp (35) for maize, and Somers and Shive (37) for soybeans, yield of barley plants was found to be determined more by the absolute levels of iron or manganese supply than by their relative proportions.…”