Mostly annual, rarely biennial herbs, shrubs, sometimes trees.
Adventitious stilt roots.
Erect, herbaceous, branched, angular or cylinderical, node and internodes clear.
Simple, alternate or opposite, exstipulate, petiolate, hairy, reticulate venation.
Head orcapitulum which may be terminal or axillary surrounded by bracts, peduncle flat on which florets are attached. Florets are surrounded by jnvolcure.
Epigynous, usually pentamerous with reduction in certain whorls, hermaphrodite or unisexual, compelete on incomplete, tubular (actinomorphic) or ligulate (zygomorphic), bracteate or ebracteate.
(A) Ray florets:
Towards periphery of head, sessile bracteate, pistillate or neutral, zygomorphic, liguate, epigynous.
Calyx: Absent or hairy pappus or scaly, persistant.
Corolla: Petals 5, gamopetalous, ligulate, strap shaped.
Gynoecium : Bicarpellary, syncarpous, ovary inferior, unilocular, one ovule in each locule, basal placentation, style simple narrow, stigma branched.
(B) Disc florets:
In the centre of head, bracteate, bisexual, actinomorphic, tubular, pentamerous, epigynous.
Calyx: Absent or pappus.
Corolla: Petals 5, gamopetalous, tubular.
Androecium: 2 stamens, epipetalous, syngenesious, dithecous, bilobed, introse, filament free.
Gynoecium: Bicarpellary, syncarpous, ovary inferior, unilocular, single ovule in the locule, basal placentation, style single, short, stigma bifid.
(C) Natural florets:
Androecium and Gynoecium both are absent. Remaining structures are similar to ray & disc florets.
(A) Plants used as food:
Lactuca sativa (Letuuce = salad), Elephentopus-Their leaves are used as vegetable. Flowers of Cynara scolymus are used as vegetable. Tubers of Helianthus tuberosus are eaten. Its seeds are also used to extract oil.
(B) Plants used in medicine:
Carthamus tinctorius-its oil is used in injuries. Leaves of Centipeda orbicularis and Xanthium stramonium are used in teeth pain. Insulin, is extracted from Cynara scolymus flowers, which is used in diabetes. Roots of Saussuarea lappa are used in gastric troubles and asthama. Santonin is prepared from the flowers of Artemisia obsinthium which is used in removing the worms from body.
(C) Ornamental Plants:
Helianthus annuus (sunflower), Tagetus erectus (Marigold), Chrysanthemum, Cosmos, Vernonica cinerea, Zinnia etc.
(D) Other commercial materials:
Perfume oil is prepared from Eclipta erecta and Malricaria chamonilla. Anti-insect oil is prepared from Pyrethrum.
Division – Angiospermae
Class – Dicotyledonae
Subclass – Gamopetalae
Series – Inferae
Order – Asterales
Family – Compositae (Asteraceae)