MALVACEAE

the mallow family, a large group of flowering plants, in the order Malvales, containing about 95 genera 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 (q.v.; Gossypium). Several species of Hibiscus produce fibres that are of lesser importance. The green fruits of okra (q.v.; 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. Thirty genera supply many species valued as ornamentals, among which are hollyhock (q.v.; Althaea), rose mallow or rose of Sharon (Hibiscus), Indian mallow (Sida), checkerbloom (Sidalcea), poppy mallow (Callirho), flowering maple (Abutilon), false mallow (Malvastrum), tree mallow (Lavatera), wax mallow (Malvaviscus), and the genera Kitaibelia and Malope. Several species of the common mallow Malva are cultivated in gardens, including musk mallow (M. moschata) and curled mallow (M. crispa). In the United States there are 27 genera; additional ones occur from Mexico into South America. Only three genera (Malva, Althaea, Lavatera) are native in Great Britain, but the family is well represented in the Mediterranean region, Africa, and Asia. The family Malvaceae includes annual and perennial herbs, shrubs, and small trees. Their leaves, which alternate on the stem, are entire (smooth-margined), toothed, or palmately lobed or divided and mostly with deciduous stipules (small appendages at the base of the leafstalk). Stellate hairs, plant hairs with the upper ends branched into starlike patterns, commonly cover some or most vegetative parts and even occur in a few species on the parts of petals exposed in bud. The flowers are regular, bisexual (sometimes functionally either male or female), and often showy. Typically the flower has five sepals and five petals, with the petals tightly twisted in bud. The petals are fused to the staminal column (i.e., the central columnar structure in the flower that bears the male structures, or stamens) at their bases and fall with the tube when the flower withers. A feature of the family is the central staminal column, surmounted by many kidney-shaped, one-celled anthers (pollen-producing structures) that open by terminal slits. The pollen grains are large, spherical, and ornamented with spines. Pollination is by insects that seek the honey secreted in pits between the bases of the petals; self-pollination also occurs through the twisting of the stigmatic arms (female pollen-receptive structures) to touch the anthers. The carpels (i.e., the ovule-bearing segments of the ovary) vary from two to many; when they number five the carpels are opposite the sepals (Hibiscus) or opposite the petals (Abutilon). In species having numerous carpels (Malva, Lavatera, Sphaeralcea), the carpels are arranged in a whorl around the top of the floral axis, with the stigmatic branches equaling or doubling the number of carpels and rising above the tip of the column. Each carpel produces from one ovule ( Malva, Malvastrum) to several ovules (Sphaeralcea, Wissadula, Gossypium, Hibiscus). The fruit is usually a one- to several-seeded schizocarp (fruit that breaks apart into one-seeded segments) but rarely, a berry in Malvaviscus, or a capsule in Hibiscus and Gossypium. Marginal hooks or elastic strands on the schizocarps, and mucilage or hairs on the seeds aid in dispersal. The genera range in size from 10 or fewer species (Anoda, Iliamna) to more than 200 (Sphaeralcea, Hibiscus). Several genera are exclusively American (Sidalcea, Callirho); others are almost worldwide in distribution (Abutilon, Hibiscus, Malva). A few species are troublesome weeds, Malva rotundifolia (called cheeses for the shape of its fruit) being the most pernicious.