The iron studied in this work occurred only at the nodal plates of corn stems, and only in the bundle sheath and outer layers of pith cells around the bundle. It accumulates as masses and crystals containing iron, which have definite optical and other properties. The crystals and masses are isotropic. The crystals belong to the cubic crystal system, and have a refractive index of n = 1.59. The Fe is present probably not as a simple compound, but as an oxide or hydroxide of Fe in solid solution in some host substance. The properties of the crystals suggest that the host substance may be protein in nature.