Knotted leaf is a malformation of corn leaves, manifested as scattered, conical or irregular emergences on the dorsal surface of the leaf. These raised regions occur most commonly on the veins. A corresponding depression occurs on the ventral surface opposite each emergence. Sections show that an emergence is a thickened fold of the leaf blade. Thickening is associated with great enlargement of mesophyll and epidermal cells. There is little or no increase in the number of layers of cells comprising the thickness of the fold. The enlarged cells are uninucleate and the relatively small nuclei are diploid
