Faculty Publications

Transectional Symmetry of Leaves

Document Type

Book Chapter

Journal/Book/Conference Title

Kaplan's Principles of Plant Morphology


Most leaves are flattened in the transverse plane, but a few species have leaves that are flattened in the median plane. This median orientation can be due to secondary twisting through the petiole, or such leaves may grow radially. A comparison of transections of the terminal buds of shoots with leaves normally flattened in the transverse plane with those congenitally flattened in the median plane. Bifacial leaves are the most typical, and occur in the widest range of species. They are leaves which are transversely flattened, dorsiventral in their lateral symmetry, and hence, by definition, have two distinctly different faces or surfaces. Window leaves are succulent, equifacial organs that expose a surface devoid of chlorophyll (the window) through which the light rays penetrate the interior of the leaf, reaching the photosynthetic tissue on both the leaf's abaxial and adaxial surfaces.


Department of Biology

Original Publication Date


DOI of published version