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form-genus Non-phylogenetic, artificial taxon of convenience. In palaeobotany the disarticulated parts of fossil plants, whose natural affinities are unknown, have been assigned to form-genera on the basis of similarities in morphology. Later discoveries may show different form-genera to have derived from the same plant, e.g. Stigmaria-type roots and Lepidodendron-type bark. See also CORDAITALES; and CALAMITES CISTIIFORMES.