X-ray Photography of Mineral Accumulations in Plants.

The accumulation of mineral salts in plants has heretofore been demonstrated mainly by microchemical means, a method which is not always satisfactory for quantitative ends, since some of the minerals may be masked through organic combinations, and since the amount of color produced, in reactions dependent on colors, is not necessarily proportional to the amount of mineral present in the tissues. In recent years HOFFER' and his coworkers have used the microchemical method to demonstrate the accumulation of iron and other elements in the nodal tissues of Zea mays in connection with corn root rot problems. The writer has employed an entirely different method, and has been able to demonstrate such mineral accumulations in the nodal tissues of sugar cane, Saccharum officinarum, with results that offer beautiful confirmation of HOFFER's discoveries with the microchemical methods in corn. The purpose of this paper is to present a few facts concerning the method of detecting mineral accumulations by means of X-rays. It is hoped thereby to stimulate more work along this line, and to encourage the use of this method in studies involving mineral deposition, and mineral translocation in plants. As time goes on X-rays have found an ever widening field of usefulness in science, -industry, and medicine. It seems quite probable that many other uses for these rays in biological work may be found. GEORGE L. CLARK, in his "Applied X-Rays, " mentions several of the less well-known applications, and says: "Although X-rays because of their short wave-length are much more able to penetrate matter than ordinary light, still they are differently absorbed by different substances; that is to say, all materials are not equally transparent to X-rays. " This fact is the basis of the science of radiography. Broadly defined, the technique consists in passing a beam of X-rays through the object to be examined, and by means of a fluoroscope, or preferably a photographic plate, record the varying intensities of the emergent rays, thereby obtaining a shadow picture of the interior of the object. The first practical uses of the X-rays were probably of a radiographic nature, and today radiography is a most useful tool for the medical and industrial diagnostician.