MALVALES

mallow order of dicotyledonous flowering plants, a division of the subclass Dilleniidae. The plants grow in various habitats throughout much of the world, and a number of members are important commercially. the mallow order of flowering plants, belonging to the class called dicotyledon (Magnoliopsida; characterized by two seed leaves). It includes five core families, together containing more than 250 genera and some 3,000 to 3,500 species. As many as five additional families are included in the order by some authorities. Representatives of this order grow in many different habitats in nearly all regions of the world. Many of its mostly woody, tropical members are commercially important. Members of the mallow family (Malvaceae) include several plants grown for their flowers, such as the hollyhock (Alcea rosea, or Althaea rosea) of temperate regions and the shrub Rose-of-China (Hibiscus rosa-chinensis), grown in most tropical regions. Economically important members include Gossypium (cotton, q.v.) and Hibiscus esculentus (okra). The bombax, or kapok tree, family (Bombacaceae) includes several important tree genera. The baobab (Adansonia digitata) of tropical Africa is remarkable in that it becomes only moderately tall but increases its girth by a very active cambial layer of cells. Many specimens measure 9 m (30 feet) in circumference. Its young leaves are edible, the pulp of its fruit is made into a refreshing drink, and its bark yields fibre. Commercially important bombacaceous trees native to the Americas are planted in many tropical regions of the world. Ochroma pyramidale produces the lightest of all timbers, balsa wood. Kapok, or silk cotton, grows from the outer layers of seeds in the fruit of Ceiba pentandra. Other important members of the Malvales include linden trees (Tilia in the Tiliaceae) and members of Sterculiaceae, whose seeds are the raw materials for beverages and confections important in world commerce. Fleshy fruits of Theobroma cacao, native from Brazil to Mexico, contain cacao nuts (seeds), which yield cocoa butter, cocoa, and chocolate. Kola nuts grow on Cola nitida and related species; their extracts are high in caffeine and the glucoside kolanin, which is used extensively in flavouring beverages. Plants of the mallow order are perpetuated almost exclusively from seeds. In several families, flowers have the five-parted pattern with differing sepals and petals. Stamens are numerous. The pistil (female) component often consists of two or more carpels containing several ovules within the ovary. Wind pollination occurs in some herbaceous representatives. The flowers of the sterculia family achieve pollination by attracting flies with their offensive odours. The flower of the wax mallow, a shrub of tropical America, is specialized for pollination by hummingbirds, and pollination by bats is the rule in the baobab and other members of the bombax family. Typically, fruits ripen dry as capsules, but in the hollyhock 15 or more carpels develop as a ring in the centre of the flower. When ripe, the individual units separate into coin-shaped segments, each containing a seed. A few members of the mallow order produce fleshy fruits. Additional reading Bertha S. Dodge, Cotton, the Plant That Would Be King (1984), a nontechnical account of the social and economic history of cotton; Paul A. Fryxell, The Natural History of the Cotton Tribe (Malvaceae, Tribe Gossypieae) (1979), a detailed but highly readable account, including discussion of characters, adaptations, and evolution, and Malvaceae of Mexico (1988), a comprehensive, technical treatment, but with general value that goes well beyond its geographical limitation; John M. Munro, Cotton, 2nd ed. (1987).