(A) A teosinte female inflorescence (left), which arises as a secondary branch from tillers, and tassel (right). (B) An ear (left) and tassel (right) of maize. Size bar in A and B is 10 cm. (C) Teosinte kernel (left) and maize kernel (right). The teosinte kernel is hidden by hardened glumes (see Glossary). The maize kernel is exposed and reveals the endosperm (En) and embryo (Em). The embryo is surrounded by the scutellum (Sc), the nutritive tissue of the cotyledon. (D) A comparison of teosinte on the left, maize on the right and the F1 of maize and teosinte in the middle. Image credits: (D) John Doebley, Department of Genetics, University of Wisconsin–Madison; all other images, Sarah Hake.