FIGURE 2.

The concept of symmetry group in mathematics. (A) F. graciliflora flowers are symmetric with respect to a set of two symmetry transformations: the identity (i.e., the transformation that does nothing) and reflection about a vertical axis. This set defines the symmetry group of Fedia that is bilateral symmetry or zygomorphy. (B) E. mediohispanicum flowers are symmetric regarding two perpendicular axes of symmetry and to a set of four symmetry transformations: the identity, reflection about the vertical left–right axis, reflection about the horizontal adaxial–abaxial axis, and rotation by 180°. These symmetry transformations are mutually equivalent when combined with each other.