Parts of a flower :

Calyx :

  • It is the outermost whorl
  • Each member called sepals.
  • Sepals are green leaf like protect the flower in the bud stage.
  • Gamosepalous: sepals are united.
  • Polysepalous: sepals are free.

Corolla :

  • It is the second whorl of a flower.
  • Each member called petal.
  • Usually brightly colored to attract insect for pollination.
  • Polypetalous: petals are free.
  • Gamopetalous: petals are united or fused.

Aestivation : the mode of arrangement of sepals or petals in the floral bud with respect to the other members of the same whorl is known as aestivation.

  • Valvate : sepals or petals in a whorl just touch one another at the margin, without overlapping. E.g. Calotropis.
  • Twisted : one margin of the appendage overlaps that of the next one and so on. E.g. china rose.
  • Imbricate : the margin of sepals or petals overlap one another but not in any particular direction as in Cassia and gulmohur.
  • Vexillary : The large petal (standard) overlaps the two lateral petals (wings) which in turn overlap the two smallest anterior petals (keel).

Androecium :

  • It is the male sex organ of the flower.
  • Composed of stamens.
  • Each stamen consists of a stalk or filament and an anther.
  • Each anther is usually bilobed and each lobe has two chambers, pollen sac.
  • Pollen grains are produced inside the pollen sacs.
  • A sterile stamen is called staminode.
  • Epipetalous: stamens attached to the petals. E.g. brinjal.
  • Epiphyllous: stamens attached to the perianth. E.g. lily.
  • Polyandrous: stamens are free.
  • Monoadelphous: stamens united into one bunch or one bundle e.g. China rose.
  • Diadelphous: stamens fused to form two bundles as in pea.
  • Polyadelphous: stamens fused to form more than two bundles as in citrus.

Gynoecium :

  • It is the female reproductive part of the flower.
  • Members are called carpel.
  • Each carpel has three parts namely stigma, style and ovary.
  • Ovary is the enlarged basal part on which lies the elongated tube, the style.
  • The stigma usually at the tip of the style.
  • Stigma is the receptive surface for pollen grain.
  • Each ovary bears one or more ovules.
  • Ovule attached to a flattened cushion-like placenta in the ovary.
  • When more than one carpel is present they may be:-
    • Apocarpous: all carpels are free. E.g. rose, lotus
    • Syncarpous: carpels fused. E.g. Tomato mustard.
  • After fertilization:-
    • Ovules develop into seed.
    • Ovary developed into fruit.

Placentation : arrangement of ovules within the ovary is known as Placentation.

  • Marginal: Placenta forms a ridge along the ventral suture of ovary.
  • Axile: Margins of carpels fuse to form central axis.
  • Parietal: Ovules develop on inner wall of ovary.
  • Free central: Ovules borne on central axis, lacking septa.
  • Basal: Placenta develops at the base of ovary.


  • It is the ripened or matured ovary after fertilization.
  • Parthenocarpic fruits developed from the ovary without fertilization.
  • Generally fruits consist of a wall or pericarp and seeds.
  • Pericarp may be dry or fleshy.
  • Pericarp differentiated into –
    • Outer epicarp.
    • Middle mesocarp.
    • Inner endocarp.
  • Fruit developed from monocarpellary superior ovary and are one seeded. Such fruit is said to be drupe as in mango and coconut.
  • Edible part of the mango is mesocarp.
  • Mesocarp of coconut is fibrous.


  • After fertilization ovules developed into seed.
  • A seed is made of seed coat and embryo.
  • The embryo is made up of
    • A radicle
    • An embryonal axis
    • One or two cotyledons.

Structure of dicotyledonous seed :

  • Outer most covering of seed is seed coat.
  • Seed coat has –
    • Outer testa
    • Inner tegmen.
  • The hilum is a scar on the seed coat, the point of attachment of developing seed with the fruit.
  • Above the hilum is a small pore called the micropyle.
  • Embryo present inside the seed coat, consists of -
    • An embryonal axis.
    • Two cotyledons
  • Cotyledons are fleshy and store reserve food.
  • At the two end of embryonal axis are present the radicle and the plumule.
  • In some seed endosperm store the reserve food as in castor.
  • Mature seed without endosperm called non-albuminous seed or non-endospermous as in bean, gram and pea.

Structure of monocotyledonous Seed :

  • Generally monocotyledonous seeds are endospermic, orchids are non-endospermic.
  • In seeds of cereals such as maize, the seed coat is fused with the fruit wall.
  • The outer covering of separates the embryo by a proteinous layer called aleurone layer.
  • Embryo is small and located one side of the endosperm and consists of
    • One large shield shaped cotyledon known as scutellum.
    • A short axis with radicle and plumule.
    • Plumule covered by a sheath called coleoptile.
    • Radicle covered by a sheath called coleorhiza.


CBSE Biology (Chapter Wise) Class XI ( By Mr. Hare Krushna Giri ) 
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