In this article we will discuss about the classification of Malvales. According to Engler, Malvales consists of five families:- 1. Tiliaceae 2. Elaeocarpaceae 3. Sterculiaceae 4. Malvaceae 5. Bombacaceae.
Contents
Family # 1. Tiliaceae:
Tiliaceae are trees and shrubs, rarely herbs; bark usually mucilaginous and with strong fibres. Leaves are alternate rarely opposite, simple, often lobed; stipules usually caducous rarely absent. Flowers are regular, bisexual, rarely unisexual, cymose and axillary, rarely solitary. Sepals 3-5, valvate, free or connate, caducous. Petals as many as sepals, imbricate, contorted or valvate, often petals absent.
Stamens usually many, free or slightly connate at base forming 5-10 bundles, often a few reduced to staminodes, a gynandrophore is sometimes present; anthers 2-celled, opening by lateral slits, introrse. A glandular disc is usually present.
Ovary superior, 2-many celled; ovules 1-many in each cell on axile placentation; style divided at the apex into as many divisions as the cells of the ovary, rarely stigma sessile. Fruit baccate or capsular; cells of the fruit often more than those of ovary by false partision, often 1-celled by reduction. Seeds solitary or many; embryo straight, usually with leafy cotyledons, endosperm usually copious.
The family consists of about 400 species under 41 genera mainly in tropical countries. Most important plants of this family are Corchorus capsularis Linn, and C. olitorius Linn, the bast fibres of which yield the jute of commerce. Grewia is a large genus with about 100 species, of which 33 are found in India. G. subinaequalis DC. is cultivated for the berries which are called “Phalsa”.
The Linden tree of Europe is Tilia europia Linn. Muntingia calabura Linn, a small spreading tree of the West Indies is planted in gardens for its beautiful foliage and white flowers. Berria cordifolia (Willd.) Burr, is a timber tree of S. India and is planted as an avenue tree in towns and cities.
The family closely resembles Malvaceae and Sterculiaceae but can be easily distinguished by free or polyadelphous stamens, 2-celled anthers, typically cymose inflorescence and the presence of a disc.
Family # 2. Elaeocarpaceae:
Elaeocarpaceae are trees and shrubs; mucilagenous cells absent. Leaves are simple, alternate or opposite, stipulate, not lobed. Flowers regular, bisexual, in axillary racemes. Sepals 4-5, valuate or imbricate, often connate. Petals 4-5, valvate, often slightly connate near base, often fringed; rarely petals absent; inserted outside a disc.
Stamens many, in groups opposite the petals with another 4-5 extra, inserted on a fleshy disc; anthers linear, opening by apical pores. Ovary superior, sessile, 2-many locular, with many ovules on axile placentation; rarely ovary 1-celled with parietal placentation; style columnar. Fruit capsular or drupaceous with a bony stone. Seeds pendulous with or without aril; endosperm small, fleshy; cotyledons flat.
The family consists of 12 genera and about 350 species occurring in tropical and subtropical countries of the world. Over 200 species are included in the genus Elaeocarpus which is well represented in India and are good timber trees. E. ganitrus Roxb. is the Rudraksha, the stones of the fruits of which are used as beads by the mendicants, and E. serratus Linn, of N. Bengal is the Jalpai or Indian Olive.
The family was included in Tiliaceae but later separated and raised to the rank of a distinct family differing from Tiliaceae by sepals not being caducous, absence of epicalyx, petals valvate and pendulous ovules. Hutchinson followed the old concept and treated both as a single family Tiliaceae.
Family # 3. Sterculiaceae:
Sterculiaceae are trees, shrubs or herbs, sometime lianes. Leaves are alternate, simple and entire or rarely palmately lobed; very rarely digitately compound; stipules caducous; often stellately hairy. Inflorescence various, often cauliflorous. Flowers are bisexual, rarely unisexual, actinomorphic or rarely zygomorphic, pentamerous, hypogynous.
Perianth often uniseriate; sepals 3-5 connate near base, lobes valvate; petals 5, often very small, sometimes absent, adnate to the base of androecium or not, contorted in bud.
Stamens 5 or 10 or more, united to form a tube, often antisepalous; staminodes present, alternating with the fertile stamens which are antipetalous; the staminodes are said to represent the outer whorl of the androecium; very rarely stamens are free; the anthers arc 2-celled, parallel or divergent.
Ovary superior, 4-5 carpelled and 4-5-celled, rarely 10-12-celled; androgynophore usually present; ovules 2-many in each chamber, as cending or horizontal on axile placentation, anatropous; styles as many as carpels, free or connate. Fruit indehiscent or capsular, sometimes separating into cocci; seeds with fleshy endosperm and flat, often folded cotyledons.
The family comprises about 50 genera and about 750 species occurring in the tropical and subtropical countries. Theobroma cacao Linn., the Cocoa or the Chocolate tree of trop. Am. belongs to this family. It produces large fruits from cauliflorous flowers, each containing many seeds, and cocoa is the powder of the roasted seeds.
The tree is now widely cultivated in S. India and Ceylon. Cola acuminata Linn, yields thein and theobromine from the seeds. Abroma augusta of N. E. India is cultivated in many places for the medicinal properties of the roots. It has drooping flowers but the flat topped fruits are erect. Pterospermum acerifolium Willd—the Muchkundo champa is a large tree with long fragrant flowers.
Heritiera littoralis Dryand. and H.fomes Bush, are the Sundari trees from which the name Sunderban has come for the littoral forests in the southern part of Bengal. Guazuma ulmifolia Lamk., Helicteris isora Link., Kleinhovia hospita Linn, and Dombeya Mastersii Hk.f. are other common trees.
As a member of the Order Malvales it has much in common with Malvaceae from which it differs by the absence of epicalyx, 2-celled anthers, an outer whorl of staminodes and usually stalked ovary.
Family # 4. Malvaceae:
Malvaceae are herbs, shrubs, or small trees; bark fibrous; mucilage present; often stellately hairy or lepidote. Leaves are alternate, palmately lobed or not, palmately veined, with free lateral, often caducous stipules. Flowers are solitary or in various types of inflorescence, axillary or terminal; epicalyx (bracteoles) usually present.
Sepals 3-5, more or less united, valvate. Petals 5, twisted in bud or often imbricate, free from each other, usually adnate at base to the staminal column. Stamens indefinite, hypogynous, united below in the form of a tube, free near the apex; anthers reniform, 1-celled; transversely attached to the filament, pollen grains characteristically spiny.
Ovary superior, usually 5-locular, often 2-locular, rarely more; ovules many, rarely only 1 on axile placentation; style enclosed in the staminal column, branched near the apex. Fruit dry, carpels separating into mericarps, or fruit capsular. Seeds usually with endosperm and folded cotyledons.
The flowers are protandrous. The immature stigmas remain hidden inside the staminal tube at first and after the dehiscence of the anthers the filaments bend down and the mature stigmas appear in the centre and spread out.
The family Malvaceae is a fairly large family with about 1500 species under 82 genera distributed mostly in the tropical countries of the world. It consists of many economically important plants and many ornamentals.
Species of Gossypium has the seeds hairy, the hairs being fine and elongated form the cotton fibre of commerce. G. arboreum Linn., G. barbadense Linn, and G. herbaceum Linn, are cultivated in India for cotton.
Hibiscus cannabinus Linn, yields a fibre from the bark similar to Jute-fibre. Abelmoschus esculentus Moench. is cultivated for its fruit viz. the Lady’s Finger used as vegetable. Hibiscus subdariffa Linn, is the Roselle, the fleshy calyx of which is used in making pickles and chutney. H. rosasinensis Linn., H. schizopetalus (Mast.) Hook. f., H. mulabilis Linn, and H. syriacus Linn, are cultivated shrubs with showy large flowers.
Althaea rosea Linn, is the Hollyhock, indigenous to Mediterranean region. Thespesia populnia Corr. the Portia Tree (Paraspipul-Beng.) is planted on road sides and parks for its beautiful large yellow flowers and glossy green foliage.
Floral range:
The epicalyx or the bracteoles vary in number and position in different tribes and genera; they are completely free from each other or are more or less united; rarely these are absent e.g. Sida, Abutilon. The median sepal is posterior in most cases and is anterior in cases of few genera.
Although the number of carpels in most genera are 5 there are only 1 or 2 in Plagianthus, while 8-10 in Malvastrum, 15-20 in Malva and numerous in Malope trifida Linn, where they are arranged vertically on an elongated thalamus; style branches as many as carpels or in Urena, Pavonia, Malachra etc. twice as many. Fruit of Malvaviscus is a berry; in other genera it is a schizocarp or capsule.
The family is divided into 4 tribes:
A. Carpels in vertical rows:
I Malopeae — Malope, Kitabelia, etc.
B. Carpels in one plane;
II Malveae — Fruit a schizocarp; styles as many as carpels: Abutilon, etc.
III Ureneae — Fruit a schizocarp; styles twice as many as carpels: Urena, etc.
IV Hibiscae — Fruit a capsule: Hibiscus, Gossypium, etc.
Family # 5. Bombacaceae:
Bombacaceae are trees, often with swollen trunk and buttressed roots, rarely shrub-like. Leaves are alternate, simple or digitate, with deciduous stipules and stellate or scurfy pubescence. Flowers are bisexual, solitary or clustered or paniculate often subtended by epicalyx. Calyx cup-shaped, 5-lobed, often truncate, leathery; lobes valvate.
Corolla of 5 petals, twisted in bud, often absent. Stamens many, filaments free or united below in the form of a tube or in distinct bundles;-anthers reniform, usually 1-celled; pollen grains smooth; often staminodes present. Ovary superior, 2-5 locular, ovules 2 or more in each cell on axile placentation; stigma capitate or lobed. Fruit usually a capsule; seeds with folded cotyledons.
Bombacaceae is allied to Malvaceae under which it was formerly included for 5-merous flowers, epicalyx often present, corolla twisted in bud, anthers usually reniform and 1- celled, and folded cotyledons.
It differs from Malvaceae in having usually smooth pollen and stamens free or united in more than one bundle; staminodes often present. The family consists of 31 genera and about 225 species distributed in the tropical countries of the world.
The family includes the Simul or Red silk-cotton tree Bombax ceiba Linn, and the White silk-cotton tree or the Kapok tree Ceiba pentandra Gaertn. The floss obtained from the fruit is used for stuffing pilows and cushions and for making life-jackets. Durio zebethinus Murr. of Malaya yields the Durion, an edible fruit with custard like flesh.
Adansonia digitata Linn, the Baobab tree of Africa lives to a great age and the trunk expands steadily to have a circumference of about 50 mtr. Ochroma lagopus Sw. is a soft-wooded tree known as the Balsawood-tree of W. Indies, the wood of which is much used for making canoes.
Segregation of Bombacaceae as a distinct family has been accepted by most botanists. Hutchinson however, places it in Tiliales, an order which besides Tiliaceae contains the families Sterculiaceae, Dirachmaceae, Scytopetalaceae and Peridiscaceae while his Malvales constists only of a single family Malvaceae.
