MALVACEAE, in botany a large and economically important family of flowering plants. It contains 45 genera with about 900 species, and occurs in all regions except the coldest, the number of species increasing as we approach the tropics. The most conspic uously useful plant is cotton (Gossypium). It is represented in Britain by three genera : Maim, mallow; Althaea, marshmallow; and Lavatera, tree-mallow. In the United States there are about 20 genera, the best known ones, after Gossypium, being Althaea (marsh-mallow and hollyhock), Malva (mallow), Sida Abutilon (Indian mallow or velvet-leaf), and Hibiscus (rose mallow, and also okra or gumbo). The plants are herbs, as in the British mal lows, or, in the warmer parts of the earth, shrubs or trees. The leaves are alternate and often palmately lobed or divided; the stipules generally fall early. The leaves and young shoots often bear stellate hairs and the tissues contain mucilage-sacs. The regular, hermaphrodite, often showy flowers are borne in the leaf axils, solitary or in fasicles, or form more or less complicated cymose arrangements. An epicalyx formed by a whorl of three or more bracteoles is generally present just beneath the calyx; sometimes, as in Abutilon, it is absent. The parts of the flowers are typically in fives; the five sepals, which have a valuate aestivation, are succeeded by five often large showy petals which are twisted in the bud; they are free to the base, where they are attached to the staminal tube and fall with it when the flower withers. The very numerous stamens are united into a tube at the base, and bear kidney-shaped one-celled anthers which open by a slit across the top. The large spherical pollen-grains are covered with spines. The carpels are one to numerous; when five in number, as in Abutilon, they are opposite the petals, or, as in Hibiscus, opposite the sepals. In the British genera and many others they are numerous, forming a whorl around the top of the axis in the centre of the flower, the united styles rising from the centre and bearing a corresponding number of stigmatic branches.
In Malope the numerous carpels are arranged one above the other in vertical rows. One or more anatropous ovules are attached to the inner angle of each carpel; they are generally ascending but sometimes pendulous or horizontal; the position may vary, as in Abutilon, in one and the same carpel.
The flowers are protandrous ; when the flower opens the unripe stigmas are hidden in the staminal tube and the anthers occupy the centre of the flower; as the anthers dehisce the filaments bend backwards and finally the ripe stigmas spread in the centre. Pol lination is effected by insects which visit the flower for the honey, which is secreted in pits one between the base of each petal and is protected from rain by hairs on the lower margin of the petals. In small pale-flowered forms, like Malva rotundifolia, which at tract few insects, self-pollination is found, the style-arms twisting later to bring the stigmatic surfaces into contact with the anthers.
Except in Malvaviscus which has a berry, the fruits are dry. In Malva (see MALLOW) and allied genera they form one-seeded schizocarps separating from the persistent central column and from each other. In Hibiscus and Gossypium (the cotton-plant), the fruit is a capsule splitting loculicidally. Distribution of the seeds is sometimes aided by hooked outgrowths on the wall of the schizocarp, or by a hairy covering on the seed, an extreme case of which is the cotton-plant where the seed is buried in a mass of long tangled hairs—the cotton. The embryo is generally large with much-folded cotyledons and little endosperm.
The largest genus, Hibiscus, contains 16o species, which are widely distributed chiefly in the tropics; H. Rosa sinensis is a well known greenhouse plant. Abutilon (q.v.) contains 120 species, mainly tropical; Lavatera, with 20 species, is chiefly Mediter ranean; Althaea has about 15 species in temperate and warm regions, A. rosea being the hollyhock (q.v.) ; Malva has about 3o species in the north-temperate zone. Several genera are largely or exclusively American.