Fig. 1. Epidermal layers of wild-type and tan mutant leaves. (A) Scanning electron micrograph (SEM) of the surface of a wild-type maize leaf primordium. Shallow indentations in the leaf surface are indicative of recent cell divisions. Horizontal arrows point to several recent transverse divisions. Vertical arrows point to several recent longitudinal divisions. (B) SEM of the surface of a tan mutant leaf primordium. Arrows point to several recent abberant divisions. Scale bars in A and B: 100 µm. (C) Epidermal peel from mature, wild-type leaf illustrating a characteristic regular cell pattern. (D) Epidermal peel from a mature, tan mutant leaf illustrating a chaotic cell pattern. Arrows point to aberrantly positioned walls in interstomatal cells that were factored into calculation of abnormality index as described in Materials and Methods. Scale bar in C: 100 µm for C and D.