DICOT FAMILIES : MALVACEAE - the cotton family

DICOT FAMILIES : MALVACEAE - the cotton family

Systematic position

Class: Dicotyledonae

Sub-class: Polypetalae

Series: Thalamiflorae

Order: Malvales

Family: Malvaceae

General characters

Distribution

This family includes about 82 genera and more than 1,500 species. The plants are cosmopolitan in distribution, more abundant in tropical and subtropical regions. In India, Malvaceae is represented by 22 genera and 125 species.

Habit

Plants may be annual herbs ( eg. Malva sylvestris) or perennial shrubs (eg. Hibiscus rosa-sinensis) or trees (eg. Thespesia populnea). The members of this family have mucilagenous substance. Stellate hairs occur on their young parts.

Root

Tap root system.

Stem

Aerial, erect (eg. Malva sylvestris), branched, woody (eg. Thespesia populnea), decumbent as in Malva rotundifolia (Thirikalamalli) and usually covered with stellate hairs.

Leaf

Petiolate, simple, entire (eg. Thespesia populnea) or palmately lobed

(eg. Gossypium arboreum), alternate, stipulate, margins usually toothed

(eg. Hibiscus rosa-sinensis) and showing reticulate venation.

Inflorescence

Solitary, terminal (eg. Malvastrum coromendelia) or solitary, axillary (eg.Thespesia populnea) or terminal or axillary cyme.eg.Pavonia odorata (Peramutti).

Flower

Bracteate or ebracteate, bracteolate or ebracteolate, pedicellate, dichlamydeous, pentamerous, complete, actinomorphic, regular, bisexual and hypogynous.

Epicalyx

Bracteoles forming a whorl outer to calyx is called epicalyx. Bracteoles 3 in Malva sylvestris, 5 to 8 in Hibiscus rosa-sinensis, 10 to 12 in Pavonia odorata and absent in Abutilon indicum.

Calyx

Sepals 5, green, gamosepalous showing valvate aestivation.

Corolla

Petals 5, coloured, polypetalous but slightly fused at the base due to adhesion with staminal tube, regular and showing twisted aestivation.

Androecium

Numerous stamens, filaments are fused to form a staminal tube around the style and monadelphous. The staminal tube is fused with the petals at their bases. Anthers are monothecous, reniform, transversely attached to filaments and transversely dehiscent.

Gynoecium

Ovary superior, two to many carpels but usually 5 to 10 carpels and syncarpous. Ovary with two to many locules. Pentacarpellary in Hibiscus rosa-sinensis, 10 in Althaea and 15 to 20 in Abutilon indicum. Number of locules usually corresponds to number of carpels. Each locule contains one to many ovules on axile placentation. Style long, slender and passes through the staminal tube ending in two to many distinct round stigmas.

Fruit

Loculicidal capsule e.g. Abelmoschus esculentus or schizocarp as in

Abutilon indicum and Sida cordifoliaI (Nilathuthi).

Seed

Endosperm is scanty, covered with hairs as in Gossypium barbadense.