Iron is a very important element in plant nutrition. This wao recognized by the first euooeseful inveetigators in thie fiald. In solution culture methods of research it ie well known that growth in plants may be inhibited by an insufficient supply of available iron. To control this available supply of iron is apparently thr* most difficult of any of the nutrient elements. The quantity lies within relatively narrow limits; both too much, and an undersupply produce physiological disturbances in the plant which is indicated by chlorosis. Among the component salts of the culture solutions are thoss which produce very Insoluble iron compounds. The solutions no* considered best soon lose most of the iron bo that frequent renewal of solution is necessary to keep up the supply of iron
