Charles Sturt University
Charles Sturt University

Common Problems

Common problems with assessing symmetry

While the flowers of most species can be easily classified as actinomorphic or zygomorphic it should be remembered there is not necessarily a clear-cut distinction between the two.

Some flowers are perfectly symmetrical and there are some very distinctive forms of zygomorphic flowers. In between there are some flowers where it can be hard to choose between the two. Most mistakes are probably made with flowers that have several free petals and the petals are relatively long and have a small point of attachment to the receptacle. In this case the petals can be pushed out of position and thus the flower appears slightly zygomorphic when it is actually actinomorphic

Another area of confusion can arise with densely packed flowers in an inflorescence, e.g. the head of the Asteraceae. Thus a daisy ‘flower’ may be interpreted by a student as a single actinomorphic flower, while the ray (ligulate) florets are zygomorphic and the disk (tubular) florets are actinomorphic.