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A subclass of the class Magnoliopsida (dicotyledons) in the division Magnoliophyta (Angiospermae), the flowering plants. The subclass consists of 8 orders, 39 families, and more than 12,000 species. The Magnoliidae are the most primitive subclass of flowering plants. In general, they have a well-developed perianth, which may or may not be numerous, centripetal stamens, and they are apocarpous. See Aristolochiales, Illiciales, Laurales, Magnoliales, Magnoliophyta, Magnoliopsida, Nymphaeales, Papaverales, Piperales, Plant kingdom, Ranunculales