MAGNOLIALES

the magnolia order of flowering plants, containing 166 genera and about 1,800 species in eight families. The order belongs to the class called dicotyledon (q.v.; characterized by two seed leaves) and consists entirely of trees and shrubs, including the ornamental magnolias. The Magnoliales are regarded as the most primitive order of angiosperms. Most trees in the group are small or medium-sized; some tall trees are found in the Magnoliaceae and Annonaceae (qq.v.) families. The Magnoliales are distributed mainly throughout wet tropical regions, with the greatest number of species in Southeast Asia and Africa. Some species are native to temperate zones in the Americas and East Asia. Trees belonging to the largest families in the order are used for timber, food, and ornamentation. Tulip tree (Liriodendron tulipifera). The Magnoliaceae family includes species that grow in temperate regions, notably the members of the genus Magnolia. About 80 species of magnolias have been described, and many are cultivated for their showy flowers. The southern magnolia (Magnolia grandiflora) is a particularly splendid evergreen, with large creamy-white blossoms. It is native to the southeastern United States and is grown as an ornamental in most warm temperate regions of the world. A hybrid species, M. soulangiana, is a small tree or shrub with large pink flowers that is widely cultivated for its beauty. The tulip tree (Liriodendron tulipifera; see photograph), also in the Magnoliaceae family, is the source of American whitewood, one of the most valuable timbers in the United States. By far the largest family in the Magnoliales order is Annonaceae, the custard apple family, whose members range throughout the tropical regions of the world. Some species in the genus Annona are cultivated for their edible fruits, including the custard apple (A. reticulata), a native of the West Indies; the sweetsop, or sugar apple (A. squamosa), found in the American tropics as well as in India and Pakistan; the cherimoya (A. cherimola) of Peru, now grown in many tropical areas; the soursop (A. muricata), a favourite in Cuba; and the alligator apple (A. glabra) of Florida. The Annonaceae include a number of species, such as lancewood and ylang-ylang (qq.v.), that produce woods, flowers, and seeds of commercial value. Polyalthia longifolia, a tall, stately tree having religious significance in Sri Lanka and India, is planted along avenues and around temples. The nutmeg family, Myristicaceae, consists of evergreen trees, often large, which are distributed throughout the tropics, many at lower elevations in rain forests. The spices nutmeg and mace are both derived from the seeds of Myristica fragrans, a native of the Indonesian archipelago. All members of the Magnoliales order are woody plants. They have simple leaves, alternately arranged, which may be evergreen. Flowers are usually bisexual (with both female and male structures), and often there is no differentiation of petals and sepals. Pollination by beetles occurs in several families. A number of structural features found in Magnoliales are regarded by botanists as primitive: flowers often consist of numerous spirally arranged free parts on an elongated floral axis; stamens (male) are frequently broad, with pollen sacs embedded in their surfaces; carpels (female) may be only slightly modified from a leaflike structure; pollen grains usually have a single groove; and seeds contain a small embryo surrounded by abundant, food-rich endosperm. It has been suggested that either the Winteraceae or the Magnoliaceae family is the most primitive living family of flowering plants. magnolia order of dicotyledonous flowering plants, a division of the subclass Magnoliidae. The order, which is generally regarded as including the most primitive angiosperms, contains 10 families, 181 genera, and about 3,050 species. All are woody shrubs, climbers, or trees. The families are Winteraceae, Degeneriaceae, Himantandraceae, Eupomatiaceae, Austrobaileyaceae, Magnoliaceae, Lactoridaceae, Annonaceae, Myristicaceae, and Canellaceae. F. Bruce Sampson Additional reading Coverage is provided by F.B. Sampson, J.B. Williams, and Poh S. Woodland, The Morphology and Taxonomic Position of Tasmannia glaucifolia (Winteraceae), a New Australian Species, Australian Journal of Botany, 36(4):395414 (1988), a rather specialized discussion of the reasons for keeping Drimys and Tasmannia as separate genera in the Winteraceae and a description of a new and unusual species of this most primitive of extant families; J.M. Miller, The Archaic Flowering Plant Family Degeneriaceae: Its Bearing on an Old Enigma, National Geographic Research, 5(2):218231 (1989), a fascinating and readable account of Degeneria, including the discovery of a new species by the author, with excellent colour illustrations; and James M. Gardiner, Magnolias (1989).