MAGNOLIIDAE

subclass of woody or herbaceous flowering plants belonging to the class Magnoliopsida. Members of the Magnoliidae are dicotyledonous plants that retain some primitive anatomic and morphological characteristics and are not closely related to more advanced groups of flowering plants. Although the subclass contains the most primitive families of flowering plants, no plant in this group is considered to be the most primitive angiosperm because none is most primitive in all its features. The fossil record suggests that the primitive woody Magnoliidae shared characteristics from which all other flowering plants evolved. Magnoliidae also contain the most primitive herbaceous angiospermsthe water lilies (Nymphaeales) and buttercups and their relatives (Ranunculales). There are 8 orders, 39 families, and approximately 12,000 species within the subclass Magnoliidae. The orders, arranged more or less from the most primitive to the most advanced, are Magnoliales, Laurales, Piperales, Aristolochiales, Illiciales, Nymphaeales, Ranunculales, and Papaverales. Such a linear sequence of orders does not imply, however, that one order has necessarily evolved from certain members of the preceding one. For example, although it is commonly considered that the Papaverales have been derived from the Ranunculales, it is also thought that the Laurales, Piperales, and Nymphaeales evolved independently from different members of the Magnoliales. The largest orders, the Magnoliales, Laurales, and Ranunculales, together contain more than two-thirds of the species in the subclass. James Edward Canright F. Bruce Sampson subclass of woody or herbaceous dicotyledonous flowering plants. Its members have regular flowers that are generally arranged separately (i.e., not in inflorescences). The subclass consists of eight orders (Magnoliales, Laurales, Piperales, Aristolochiales, Illiciales, Nymphaeales, Ranunculales, and Papaverales), which together contain 39 families and about 12,000 species. One feature of some Magnoliidae is a spiral arrangement of the floral parts, which is a primitive feature among the flowering plants. The perianth is often not differentiated into distinct petals and sepals, and the stamens are commonly numerous and often leaflike in more primitive members, although distinct filaments and anthers are seen in others. The vast majority of species in the subclass Magnoliidae are found in the orders Magnoliales, Laurales, and Ranunculales. Additional reading Coverage is provided by Peter K. Endress, Evolution of Reproductive Structures and Functions in Primitive Angiosperms (Magnoliidae), Memoirs of the New York Botanical Garden, 55:534 (February 1990), an extremely useful summary.