MALVACEAE - the cotton family Notes
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.
