Wednesday, 10 September 2008
FAMILY OF THE WEEK : MALVACEAE
In India the family is representaed by 22 genera and 110 species occurring mostly in warmer parts.Benthem and Hooker divided the family into four subfamilies, Malveae,Ureneae,Hibisceae and Bombacaceae. Bommbacaceae is not covered here as it has been explained elsewhere.
Vegetative characters :
The members are mostly annual or perennial herbs, but in the tropics they are shrubs or rarely soft wooded trees. The stem is fibrous with inner bark often tenacious. The herbaceous portions are often more or less covered with stellate hairs.
The leaves are alternate, simple,entire.
Inflorescence and flowers :
The inflorescences are either axillary, solitary, or fascicled and often form long terminal racemes.
The flowers are hermaphrodite or rarely unisexual or polygamous, actinomorphic, pentamerous and hypogynous.
The calyx is frequently subtended by an involucre of bracteoles which form the epicalyx. It protects the younf flower bud. The calyx is usually of five, free or connate sepals which show valvate aestivation. The corolla has five petals which are often large and showy, free or basally connate with the staminal coloumn as in Hibiscus. The petals show twisted or imbricate aestivation.
The androecium has numerous stamens which are monadelphous. The filaments are united to form a staminal coloumn around the ovary. The staminal cploumn is divided at the apex and bears reniform monothecous anthers.The pollen grains are covered by spines.
The gynoecium is of two to many fused carpels which are arranged in a whorl around the central axis. The ovary is superior.
Fruits and seeds :
The fruit is loculicidal capsule as in Hibiscus and gossipium or more often it is a dry indehiscent, In sida, Malva and Abutilon schizocarps separate from one another and from the persistent central axis and each one seeded or occasionally two to many seeded as in some species of Abutilon. The seeds are reniform or obovoid with scanty endosperm . They are often pubescent or densely clothed with wooly hairs as in Gossipium.
The flowers are mostly insect pollinated.The seeds of gossipium are dispersed by wind. In some species such as Urena lobata the seeds have hooked spines which are dispersed by adhesion to animals and human.
Gossipium (Cotton):(Marathi: Kapus)extensively cultivated in the tropics for fibre. The cultivated forms arise mainly from G.barbadense and G.hirsutum(America) and G.arboreum and G.hirbaceum in India, Egypt and other countries.
Several species are grown as ornamentals:
Hibiscus esculentus(Lady's finger,Okra,Bhendi) used as vegetable.
Posted by SATISFIED at 18:58