Family Compositae – Description in Semi-Technical Terms

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Family-CompositaeBotany | Biology Notes
Family – Compositae
General Description in Semi-technical Terms
For: Science Class 11

The compositae family is also known as sunflower family. This is the largest family of angiosperm. There are about 1000 genera and 2300 species. They are cosmopolitan in distribution. Some economically important members are:

Helianthus annus, SUNFLOWER – Important for oil
Chrysanthamum indicum, CHRYSANTHAMUM – Important ornamental flower
Tagetes erecta, HAJARIPHOOL – Important ornamental flower
Artemesia indica, TITEPATI – Important medicine for skin disease and antihelminthic
Azeratum conyzoides, GANDHE – important medicine for cut and wound
Carthamus tinctorius. KUSUM – important medicine

Habit/Habitat: Mostly they are annual herbs or perennial shrubs, some are climbers, wild or cultivated, ornamental, few are trees (Veronica arborea), hydrophytic, mesophytic or xerophytic.
Root: Tap root, branched or adventitious
Stem: Erect or prostrate, few are climbing, herbaceous or woody, solid or fistular, branched, cylindrical or angular, hairy or glabrous, sometimes underground or stem unbranched.
Leaf: Exstipulate or stipulate, petiolate, cauline and ramal, alternate or opposite or whorled, simple or compound, pinnately compound, alnceolate, serrate or entire, acute, unicostate, reticulate venation, sometimes leaves are modified into spines or reduced.
Inflorescence: Head or capitulum, Head consists of two types of flowers Ray florets and disc florets, Head is surrounded by involucre of bracts

Flowers: 

Ray florets

bracteate, ebracteolate, sessile, zygomorphic, unisexual, incomplete, epigynous, ligulate
Calyx: Rudimentary, sometimes absent or hairy or scaly
Corolla: Petals – 3-5, gamopetalous, bilabiate, valvet aestivation.
Androecium : absent
Gynoecium: carpels – 2, bicarpellary, syncarpous, Ovary – inferior, unilocular, basal placentation, Style – Single, Stigma – bifid
Fruit: Cypsela
Seed: nonendospermic, dicotyledonous
Floral Formula : ______________
Floral diagram : _________________

Disc Florets
Bracteate, sessile, ebractiolate, actinomorphic, hermaphrodite, pentamerous, epgynous, sometimes unisexual.
calyx: Reduced or absent or sometimes hair like or scale like – 2-5.
Corolla: Petals – 5, gamopetalous, tubular, bilobed, valvet aestivation.
Androecium: stamens – 5, polyandrous, syngenesious, epipetalous, Anther – dithecus, basifixed, introse.
gynoecium: Carpels – 2, bicarpellary, syncarpous, Ovary – inferiorm unilocular, basal placentation, Style-long, Stigma-bifid.
Fruit: cypsela
Seed: dicotyledenous, nonendospermic
Floral formula : ______________
Floral diagram : _______________

Systemic position:
Class : Dicotyledonae
———-Subclass : Gamopetalous
—————Series : Inferae
———————Order : Asterales
————————–Family : Compositae

Diagnostic characters: Leaves simple or comound, opposite or whorled. Inflorescence Head or capitulum. Flower – bracteate, epigynous, Two types-ray and disc florets. Sepals rudimentary or hairy or scaly, 2-5. Petals – 2-5, gamopetalous. Stamens absent in ray florets but stamens – 5 in disc florets, polyandrous, syngenesious. Carpels – 2, bicarpellary, syncarpous. Ovary – inferior, uniclocular, basal placentation, Stigma-bifid.

Posted By : Hari Prasad Chaudhary | Comment RSS | Category : Class XI, HSEB Notes
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