Zygomorphic Flower

a flower through which one can pass only one plane of symmetry that will divide it into two parts. (The symmetry is established according to the perianth, without consideration of the location of its internal parts.) Three types of zygomorphic flowers are distinguished: typically zygomorphic (the plane of symmetry passes through the pedicel and axis of the inflorescence—that is, it coincides with the median plane, as in Leguminosae and Labiatae), transversely zygomorphic (the plane of symmetry is perpendicular to the median plane, as in Corydalis and Fumaria), and obliquely zygomorphic (the plane of symmetry lies at an acute angle to the median plane, as in horse chestnut). Zygomorphic flowers appeared as a result of a plant’s adaptation to being pollinated by certain insects which penetrate the flower from only one position and always touch the stamens and the stigma of the pistil in the process.