Malvaceae

▪ plant family

 the hibiscus, or mallow, family, in the order Malvales, containing 243 genera and at least 4,225 species of herbs, shrubs, and trees. Representatives occur in all except the coldest parts of the world but are most numerous in the tropics. Economically, the most important member of the family is cotton (Gossypium). Several species of Hibiscus produce fibres that are of lesser importance. The green fruits of okra (H. esculentus) are cooked and eaten, and the mucilage secreted in tissues of some species has been used in certain confections and for other purposes.

      Genera now included in Malvaceae were long thought to be very closely related, but, until DNA studies were done at the end of the 20th century, they were placed in four different families: Malvaceae, Bombacaceae, Tiliaceae, and Sterculiaceae, this group of families alone constituting Malvales for some earlier botanists. DNA evidence has shown that many of the genera in these families are interdigitated, a finding used for including them in a larger, single family rather than maintaining artificial lineages (ones that do not share a common ancestor).

 Hibiscus (550 species), Pavonia (150 species), and Sida (200 species) are all widely distributed, Sida being particularly diverse in the New World. Nototriche (100 species) is native to South America. An epicalyx is particularly common in this group of genera. The stamens are fused into a tube. They are temperate to tropical plants, often herbs or shrubs, with spiny pollen. Many are ornamental, a number yield fibres, and okra and gumbo are the immature fruits of H. esculentus. Cotton comes from the seed hairs of species of Gossypium (40 species; tropical to warm temperate); these hairs are very fine and are almost pure cellulose.

 Hairs from the ovary wall from genera such as the Paleotropical Bombax (20 species) and the pantropical Ceiba (11 species) yield kapok. Ochroma is the source of balsa wood. Several genera, including the Old World Adansonia (e.g., A. digitata, the baobab), are cultivated for their flowers and the distinctive appearance of the trees. Members of these genera are typically stout trees with thin, often green bark, and several have stout spines. The leaves are frequently palmately compound.

      Grewia (290 species) is mostly Neotropical, with about 2 species from the Paleotropics. Microcos (60 species) is native to Indo-Malesia. Corchorus (40–100 species) and Triumfetta (about 150 species) are pantropical. Corchorus is a source of jute. Sparmannia, with three species from Africa and Madagascar, is an ornamental. Byttneria (135 species) is pantropical, but especially South American; the genus used to be part of Sterculiaceae. Hermannia (100 species) is especially common in Africa. Melochia (55 species) is mainly New World. Ayenia (70 species) is found in tropical and warm temperate regions of the New World.

      Theobroma (20 species) is native to the Neotropics. The flowers are often very distinctive. The petals of this genus are often broad at the base, then narrowed, and finally with another broader, often dangling portion. There are often fewer than 15 stamens, but petaloid staminodes are developed. As a result, the flowers are often quite complex and are pollinated by small flies, midges, and such that are attracted in part by the dangling petals. T. cacao is the main source of cocoa, and the fruits of other species from the Amazonian region yield delicious pulp for juices or sorbets (T. grandiflorum).

 The pantropical Sterculia (150 species) and the African Cola (125 species) were part of the former family Sterculiaceae, whose members were noted for having separate male and female flowers borne in often quite large and branched inflorescences. These genera have sepals that are fused; there are no petals; and the stamens and ovary are borne on a stalk. The individual carpels are free. Caffeine-containing seeds of Cola are used in cola drinks.

      Tilia (23 species) grows in north temperate regions. Certain Tilia species (known as linden or basswood trees in the United States and as lime trees in England) are often planted along streets for their beautifully scented flowers or grown for their valuable wood. Dombeya (225 species) is extremely diverse on Madagascar; it is sometimes cultivated for its flowers. Melhania (60 species) grows in the Paleotropics. Helicteres (40 species) grows from Asia to the New World. Durio (27 species) grows from Southeast Asia to western Malesia. The famous durian fruits are obtained from D. zibethinus. The massive spiny fruits are opened to reveal large seeds surrounded by a creamy fleshy covering, or aril. Some people cannot stand the smell or taste of durians, while others think they are one of the world's finest delicacies.

Paul E. Berry

 

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