a. Bot. [f. Gr. ζυγόν yoke + μορφή form + -IC.] Applied to a flower that is symmetrical about a single plane, i.e., divisible into similar lateral halves in only one way; = MONOSYMMETRICAL. Also Zygomorphous; opp. to ACTINOMORPHOUS. So Zygomorphism, the character of being zygomorphic.
1875. Bennett & Dyer, trans. Sachs’ Bot., 526. In Orchids both whorls are developed in a petaloid, and like the whole flower in a zygomorphic or monosymmetrical manner. Ibid., 534. The zygomorphism of the flower.
1879. A. Gray, Struct. Bot., 175, note. Both these forms [sc. monosymmetrical and polysymmetrical] have a more expressive and older terminology, adopted by Eichler, viz.:—Zygomorphous, for flowers, or other structures, which can be bisected in one plane,… (median zygomorphous, when this is a median or antero-posterior plane,… transverse zygomorphous, when the plane of section is transverse or at right angles to the median).
