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MALVACEAE

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Originally appearing in Volume V17, Page 518 of the 1911 Encyclopedia Britannica.
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MALVACEAE , in See also:

botany, an See also:order of See also:Dicotyledons belonging to the See also:series Columniferae, to which belong also the orders Tiliaceae (containing Tilia, the See also:lime-See also:tree), Bombaceae (containing Adansonia, the See also:baobab), Sterculiaceae (containing Theobroma, See also:cocoa, and Colo, cola-See also:nut). It contains 39 genera with about 300 See also:species, and occurs in all regions except the coldest, the number of species increasing as we approach the tropics. It is represented in See also:Britain by three genera: Malva, See also:mallow; See also:Althaea, See also:marsh-mallow; and Lavatera, tree-mallow. The See also:plants are herbs, as in the See also:British mallows, or, in the warmer parts of the See also:earth, shrubs or trees. The leaves are alternate and often palmately lobed or divided; the stipules generally fall See also:early. The leaves and See also:young shoots often See also:bear stellate hairs and the tissues contain See also:mucilage-sacs. The See also:regular, hermaphrodite, often showy See also:flowers are See also:borne in the See also:leaf-axils, See also:soli- tary or in fasicles, or See also:form more or less complicated cymose arrangements. An epicalyx (see MALLOW, See also:figs. 3, 4), formed by a whorl of three or more bracteoles is generally See also:present just beneath the calyx; sometimes, as in See also:Abutilon, it is absent. The parts of the flowers are typically a, Stamens. b, Bract. in See also:fives (fig. 1); the five sepals, g, See also:Pistil of carpels. which have a valvate See also:aestivation, i, Epicalyx, formed from an in-are succeeded by five often large volucre of bracteoles.

showy petals which are See also:

twisted p ' Petals. s, Sepals. in the bud; they are See also:free to the See also:base, where they are attached to the staminal See also:tube and fall with it when the See also:flower withers. The very numerous stamens are regarded as arising from the branching of a whorl of five opposite the petals; they are See also:united into a tube at the base, and bear See also:kidney-shaped one-celled anthers which open by a slit across the See also:top (fig. 2). The large spherical See also:pollen-grains are cov- ered 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 See also:round the top 1, Anther. of the See also:axis in the centre of the 2 Pollen See also:grain of See also:Hollyhock (Althaea rosea) enlarged. The pollen grain bears numerous spines, the dark spots indicate thin places in the extine. b 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 See also:vertical rows. One or more anatropous ovules are attached to the inner See also:angle of each carpel; they are generally ascending but sometimes pendulous or See also:horizontal; the position may vary, as in Abutilon, in one and the same carpel.

The flowers are proterandrous; 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 See also:

bend backwards and finally the ripe stigmas spread in the centre. See also:Pollination is effected by See also:insects which visit the flower for the See also:honey, which is secreted in pits one between the base of each petal and is protected from See also:rain by hairs on the See also:lower margin of the petals. In small See also:pale-flowered forms, like Malva rotundifolia, which attract few insects, self-pollination has been observed, the See also:style-arms twisting to bring the stigmatic surfaces into contact with the anthers. Except in Malvaviscus which has a See also:berry, the fruits are dry. In Malva (see MALLOW) and allied genera they form one-seeded schizocarps separating from the persistent central See also:column and from each other. In Hibiscus and Gossypium (See also:cotton-plant, q.v.), the See also:fruit is a See also:capsule splitting loculicidally. See also:Distribution of the seeds is sometimes aided by hooked outgrowths on the See also:wall of the schizocarp, or by a hairy covering on the See also:seed, an extreme See also:case of which is the cotton-plant where the seed is buried in a See also:mass of See also:long tangled hairs—the cotton. The embryo is generally large with much-folded cotyledons and a small amount of endosperm. The largest genus, Hibiscus, contains 150 species, which are widely distributed chiefly in the tropics; H. rosasinensis is a well-known greenhouse plant. Abutilon (q.v.) contains 8o species, mainly tropical; Lavatera, with 20 species, is chiefly Mediterranean; Althaea has about 15 species in temperate and warm regions, A. rosea being the hollyhock (q.v.); Malva has about 30 species in the See also:north-temperate See also:zone. Several genera are largely or exclusively See also:American.

End of Article: MALVACEAE

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