Floral symmetry refers to whether, and how, a flower can be divided into 2 or more identical or mirror-image parts.
Most flowers are actinomorphic, meaning they can be divided into symmetrical halves by more than one longitudinal plane passing through the axis. Examples are flowers of Liliaceae, Ranunculaceae.
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However, some familiar and seemingly actinomorphic flowers, such as those from Asteraceae, are actually clusters of tiny zygomorphic flowers arranged into a radially symmetric inflorescence.
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Zygomorphic flowers can be divided by only a single plane into 2 mirror-image halves. Examples are flowers of Zingiberales, Lamiales ( Scorphulariaceae, Gesneriaceae )
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Actinomorphic flowers are basal angiosperm character ; zygomorphic flowers are a derived character that has evolved many times.
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