A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants. The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs. In addition to facilitating the reproduction of flowering plants, flowers have long been admired and used by humans to bring beauty to their environment, and also as objects of romance, ritual, religion, medicine and as a source of food. In this lesson you will learn about : 1) Flower - Definition & Functions 2) Floral Symmetry 3) Pedicellate & Sessile Flowers 4) Insertion of Floral Leaves on the Thalamus 5) Parts of a Flower 6) Some Important Terms related to Flowers 7) Floral Whorls - Calyx, Corolla, Androecium and Gynoecium 8) Placentation 9) Inflorescenece I hope this document is helpful to you. Please share the document with your friends if you think this will benefit them. Get ready for the next lesson. Thanks.

1. The Flower

2. Introduction
A flower is a reproductive part of an angiospermic plant. It
is considered to be a modified shoot having nodes and
internodes and the leaves are modified into floral
structures.
Functions of Flower :
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It helps in the sexual reproduction of the plant by
producing male gametes (pollen grains) and the female
gametes (egg cell). The union of the two gametes
results in fertilization.
It helps in the process of pollination, i.e., transference
of pollen grain from the anthers to the stigma of the
same or of the different flower.
It help in the development of seeds and fruits.
It also helps in the dispersal of seeds and fruits.
Asymmetrical
Flower
In this type, the
flower cannot be
divided into similar
halves along any
vertical plane.

3. The flower is commonly borne on short or long stalk called
the pedicel (stalked or pedicellate flower). Some flowers
may be without stalk (sessile flower).
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Receptacle
Stalk
The tip of flower stalk may be expanded to form a cup-
shaped receptacle (thalamus).
Introduction

4. Hypogyny :
When the thalamus is convex or elongated, the carpel occupies
the top most position on it. The other floral members (sepals,
petals, and stamens) are placed below them. This mode of
arrangement is called hypogyny. The flower is described as
hypogynous. The ovary is known as superior.
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Insertion of Floral Leaves on the Thalamus
Perigyny :
In this condition, the receptacle is flat or slightly cup-shaped.
The carpels are situated at its centre and other floral
members are inserted on its margin. This mode of arrangement
is called perigyny. The flower is known as perigynous. In this
case, the ovary is still described as half inferior.
Epigyny :
When the thalamus is cup shaped, the lower part of the ovary
is situated at the bottom of the cup and also fused with the
inner wall of thalamus. The other floral members appear to be
inserted upon the ovary. This mode on arrangement is
called epigyny. Then the flower is said to be epigynous. the
ovary is said to be inferior.

5. A typical angiospermic flower consists of four whorls of floral
appendages attached on the receptacle :
✓ Calyx : It is the outermost whorl of the flower. It is composed
of leaf like green sepals. The sepals are essentially green in
colour but in some cases they are coloured like petals. Such a
condition of calyx is called petaloid.
✓ Corolla : This is the second whorl of the flower and consists of
a number of petals. Petals are generally brightly coloured and
sometimes fragrant which make the flower to become
attractive.
✓ Androecium : It is the third whorl of flower and is the male
reproductive organ consisting of stamens. Each stamen is made
of filament and anther. The filament supports anther at its tip.
✓ Gynoecium : This is the last and the fourth whorl of flower
and is the female reproductive organ of the flower. It occupies
the central position on the receptacle and composed of ovary,
style and stigma and the component parts are called carpels.
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Parts of a Flower
A complete (or perfect) flower is one
which contains all four floral structures.
If one or more sets of floral structures
are missing, the flower is called
incomplete (or imperfect).

6. Essential & Non-essential Parts of a Flower
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Essential (reproductive) parts of a flower are those that are
directly associated with reproduction.
E.g., Stamen and Carpel (or Pistil).
Non-essential (accessory) parts are those which either
protect the reproductive parts of the flower or make the
flower attractive for pollination.
E.g., Sepals and Petals.
In some flowers calyx and corolla are undifferentiated and
cannot be distinguished. They are termed perianth.
When the perianth is non-green it is described as petaloid.
When the perianth is green like the sepals, it is described as
sepaloid perianth.

7. Other Important Terms
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In a flower, if all the four whorls, i.e., calyx, corolla,
androecium and gynoecium are present, the flower is said to be
complete.
Complete flower :
If one or more floral whorl is lacking in the flower, the flower
is said to be incomplete.
Incomplete flower :
Pistillate – If the staminate whorl (androecium) is absent or
non-functional, the flower is said to be pistillate. The non-
functional stamens are called staminodia.
Staminate – In this type of flower, the pistil or carpel
(gynoecium) is either totally lacking or non-functional. The non-
functional gynoecium is known as pistillode.
Neuter – When both, the staminate and pistillate whorls are
lacking, the flower is called neuter, for example, ray floret of
sunflower.
Bisexual or Hermaphrodite :
These are flowers having both the essential whorls, i.e., the
androecium and the gynoecium.
Unisexual :
If either of the essential whorls (i.e., androecium or gynoecium)
is lacking, the flower is said to be unisexual.
Monoecious – The male and female flowers are borne on the
same plant, for example, gourd, maize, cucumber.
Dioecious – The male and female flowers are borne on separate
plants, for example, mulberry, palm, papaya.
Naked :
This condition arises when the flower is completely devoid of
petals and sepals, for example, betel.

8. Calyx
The calyx composed of sepals is usually green (sepaloid) and
sometimes otherwise coloured (petaloid). It forms the
outermost non-essential whorl of the flower and protects the
flower in the bud stage. Being green, it also manufacture food
by photosynthesis.
The calyx may be :
Gamosepalous – the sepals are more or less united.
Polysepalous – the sepals are free.
Generally, the calyx withers off when the fruit is formed.
Sometimes it remains attached as in tomato and brinjal. Such a
calyx is called a persistent calyx.
Functions of the calyx :
Protects the flower in the bud stage.
Prepares food for the plant by photosynthesis.
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In some plants a whorl of green
sepals like structure is present at
the base of calyx called epicalyx.
Epicalyx is considered a whorl of
the bracteoles and mostly found
in the flowers of family Malvaceae.
Calyx
Epicalyx
Epicalyx

9. The corolla forms the whorl inner to calyx. Together with the
calyx, it protects the inner essential whorls, the stamens and
pistil. The petals of the corolla, like the calyx, may be united to
each other or may be free.
The corolla may be :
Gamopetalous – the petals are united.
Polypetalous – the petals are free.
The corolla is generally large and showy and assumes various
shapes adapted to attract insects and bring about pollination.
Functions of the corolla :
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Corolla
They attract insects for pollination as they are generally
bright and showy.
In the bud stage, the corolla together with the calyx,
protects the inner essential whorls.
Bracts Nectaries
A modified leaf or scale, typically small,
with a flower or flower cluster in its axil.
Bracts are sometimes larger and more
brightly coloured than the true flower.
The nectaries make nectar.
They are in the centre of the flower.
Nectar is a sweet substance, which
insects drink to give them energy.

10. The androecium is the male reproductive whorl of a flower,
inner to the corolla. It is composed of a number of stamens,
each of which consists of a filament and anther.
The anther is usually two lobed. Each lobe has two pollen sacs.
Within the pollen sacs are contained pollen grains. When fully
matured the pollen sacs rupture to liberate pollen grains.
The pollen grains are generally powdery particles of different
shapes and sizes. Each pollen has two coats – the exine (tough,
cutinized outer protective coat) and the intine (thin delicate
cellulose layer lying internal to the exine).
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Androecium
The filaments may be free from each other and other
structures or they may be fused with each other or fused with
the petals or gynoecium. They may also vary in size.

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Types of Androecium
According to the length of the filament :
According to the number of stamens :

12. How to remember the above three terms ?
Mono-,Di- and Poly- respectively mean single, two and several.
Adelphous literally means “group of brothers”, here referring to the part from which the anthers
grow out in bundles. Thus the bundle of anthers arising from a single part (monadelphous), the
bundles from two parts (diadelphous) and from several parts (polyadelphous).
Adelphous :
The stamens are fused by their filaments only. The anthers are
free. Fusion of filaments may produce a single group
(monadelphous, e.g., china rose), two groups (diadelphous, e.g.,
pea) or many groups (polyadelphous, e.g., citrus).
Syngenesious (= Synantherous) :
Stamens are fused by anthers only. The filaments are free. The
fused anthers form a ring around the gynoecium, e.g., sunflower.
Synandrous :
Stamens are fused by both their filaments as well as anthers,
e.g., pumpkin.
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Forms of Cohesion (Fusion) of Stamens

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Insertion and Adhesion of Stamens
Fixation of Anthers
Basifixed – Filament attached to the base of the anther.
Dorsifixed - Filament attached to the dorsal (back) side of
the anther.
Adnate - Filament attached along the entire length of anther.
Versatile – Filament attached to a point on the back or base of
anther so as to let it swing freely.
Divergent – When two anther lobes separate due to enlarged
connective.
Distractile – When two anther lobes are far apart.

14. Gynoecium
The gynoecium or pistil is the female reproductive part of the
flower and forms the innermost whorl. The pistil is composed of
one or more carpels.
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Stigma
Terminal knob-like
part of the carpel.
Style
Tubular stalk
connecting the stigma
and the ovary.
Ovary
Swollen basal portion.
The inner cavity may
contains one or more
chambers. Each
chamber contains one
or more ovules.
Parts

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Placentation
The arrangement of ovules within the ovary is known as
placentation.
Marginal – The placenta forms a ridge along the ventral
suture of the ovary and the ovules are borne on this ridge
forming two rows. e.g., pea.
Axile – When the placenta is axial and the ovules are
attached to it in a multilocular ovary. e.g., china rose,
tomato and lemon.
Parietal – the ovules develop on the inner wall of the ovary
or on peripheral part. Ovary is one-chambered but it
becomes two chambered due to the formation of the false
septum(replum) e.g., mustard and Argemone.
Basal – the placenta develops at the base of ovary and a
single ovule is attached to it. e.g., sunflower, marigold.
Free Central – When the ovules are borne on central axis
and septa are absent. e.g., Dianthus, Primrose.
Ovules turn into seeds in the mature fruit
(transformed ovary). their different
arrangements can be seen in fruits such as
those of pea, tomato, mango, lotus, etc.
Types of Placentation :

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Inflorescence is the mode of arrangement of flowers on the
axis of the plant.
Types of Inflorescence :
Inflorescence
The flowers may be arranged in several different ways in different plants, this manner
of arrangement is termed as inflorescence.