2. THE FLOWER
A flower is define as a
modified reproductive shoot
of determinant growth,
consisting either only stamens
(microsporophyll) or Carpel’s
(megasporophylls) or both and
may or may not be associated
with accessory parts like
sepal, petals to produce fruit
3. Different term related to flower.
Complete Flower: :A complete
flower is a flower that has all
four parts of the flower (sepals,
petals, androecium and
Incomplete flower: A complete
flower contains all four organs,
while an incomplete flower is
missing at least one. A bisexual
(or “perfect”) flower has both
stamens and carpels, and a
unisexual (or “imperfect”) flower
either lacks stamens (and is
called carpellate) or lacks
carpels (and is called
4. Symmetry of flower
(regular): Flowers that are
radially symmetrical so that they are
able to be bisected into similar
halves in more than one vertical
plane, forming mirror images.
• Zygomorphic flower
(irregular): Flowers that are
bilaterally symmetrical so that they
are able to be bisected into similar
halves in only one plane, forming
5. Cyclic(most of angiosperms): A flower whose parts are
arranged in a whorl. Cyclic flowers are characteristic of
most flowering plants, including those of the families
Liliaceae, Caryophyllaceae, and Solanaceae.
• Acyclic ( Eupomatia): A flowers whose parts are
arranged in spirals rather than in whorls, as in
• spirocyclic flower( Nymphaeaceae): It is
flower where half of the members are
arranged spirally and half of members
arranged in whorl manner.
7. Pistillate and staminate flower
• Unisexual or
Imperfect flowers that
bear stamens only
are called staminate
flowers or male
• Unisexual or
Imperfect flowers that
bear pistils only are
flowers or female
8. • Monoecious plants are those in which
both the staminate and pistillate flowers
are borne on the same plant. Cucerbita.
• Species in which the two imperfect flowers
are borne separately in different plants are
called dioecious. Borassus flabellifer.
• Some plant bear male, female and
bisexual flower are called polygamous
flower. Eg Litchi sinensis.
• Perianth of a flower
• The perianth is the outer envelope enclosing a flower and is made
up of either:
• an outer calyx and inner corolla;
• a calyx or corolla; or
• calyx and corolla combined and undifferentiated from one another.
• The corolla of a flower is divided up into
petals whereas the calyx is made up or
– If the calyx and corolla are combined into
one undifferentiated unit, then the
individual parts are referred to as tepals.
11. Parts of typical flower
• A flower consist of an axis known as
thalamus, on which four different sets of floral
parts are inserted.
a. Thalamus: The thalamus is the receptacle or
terminal part of the axis of a flower. Some
times it is long , showing distinct internode.
• In many Plant species, the calyx consists of
green leaf-like structures, the sepals, which
protect the delicate inner parts of the flower
while it is developing and prevent it from
desiccating. The sepals may be fused or free
and symmetrical or assymetrical. In some plant
families likeLiliaceae it is not possible to
distinguish between sepal and petals and these
structures are called tepals.
• In many species, the corolla which
consists of the whorl of petals, is the most
obvious part of the flower. Some flowers
have large, showy petals but in some
families such as the grasses the petals
have become very reduced. It is also free
or fused and termed as polypetalous and
14. AESTIVATION of floral parts.
It is the mode of arrangement of accessory floral
member ( sepal , petal & perianth ) with respect to one
another in a flower bud. These are following types.
15. • Valvate: In this type, the margin of sepals or
petals simply touch each other but not overlap.
Twisted (contorted): In this case sepals or petals
are arranged in such way that their one margin
overlaps the margin of the next one and the other
margin is overlapped by margin of another.
Imbricate: In this case out of five accessory
members one is purely internal, one is external
and other three partly internal and partly external.
16. Quincuncial: In this case out of five accessory
member two is purely internal, two are external
and one partly internal and partly external e.g.
Vexillery: It is a type of imbricate aestivation,
here out of five petals the odd posterior one
(standard) is largest and outermost, it overlaps the
two lateral petals (wings) and the lateral petals
again in turn partly overlap the two smallest and
innermost petals (keel).
17. Androecium: Depending on the numbers
and arrangement of stamen, it is classified in
to following groups.
– Diplostemonous: stamens
occurs in two whorl. And
outer one is alternate with
petals and consequently
opposite to sepals. Cassia
– Obdiplostemonous: When
stamens of outer whorl are
opposite with petals and
consequently alternate to
sepals. Oxalis sp
– Isostemony: When all
stamens are in one whorl and
are equal to the number of
sepals and petals.
– Tetradynamous: Stamens are
six. Outer two are shorter and
inner four are longer or vice
versa (A2+4) Cruciferae
– Didynamous: Stamen four.
Two are long and two are
19. Union of stamen
The union of stamens takes place either among
themselves (cohesion) or with other whorls
– Adhesion of stamens : Stamens may unite
with other floral whorls like Perianth, petals
or gynoecium. Based on the floral organ
involved in the union with stamens, the
adhesion may be of the following types :
20. Adhesion of stamens
• Epiphyllous : Stamens
unite with perianth. e.g.,
• Epipetalous : Stamens
unite with petals. e.g.,
• Gynandrous : Stamens
unite with gynoecium. It
is also called
21. Cohesion of Stamens
Usually three types of cohesion among stamens occur. They are
1. Adelphous: Anthers remain
free and filaments are united.
Adelphous condition can be
to form 1 bundle, e.g.,
form 2 bundles, e.g., Pea
United into more than two
bundles, e.g., Lemon
23. Attachment of anther to the
• Innate or Basifixed: When the
filament is firmly attached to the
base of the anther. Solanum sp
• Adnate: When filament running
the whole length of the anther
from the base to apex. Michelia
• Dorsifixed: When the filament
attached to the back of anther.
• Versatile: Filament attached to
the back of anther at a point only
, so that the later can swing
24. Dehiscence pattern of Stamen
• (i) Porous: Pollens
released through pores,
• (ii) Longitudinal:
through the longitudinal
• slit of another lobes, e.g.,
China rose, Cotton
o Gynoecium : The gynoecium or pistil is the fourth
essential whorl of the flower and may be made up of
one or more carpels (megasporophylls).
o A carpel has three distinct part, namely ovary, style
and stigma. The lower most swollen fertile part of the
carpel is the ovary. It encloses ovules. Above the
ovary elongated thread like structure attached to the
apex of the ovary, the style. The style end with a
round, sticky stigma.
o A sterile pistil is known pistillode. The number of
carpels in a gynoecium vary in different flowers.
Accordingly the gynoecium may be described as
26. – Monocarpellary : It is a
ovary with a single carpel,
– Bicarpellary : It is presence
of two carpels in a ovary,
– Tricarpellary : It is presence
of three carpels, e.g., Cocos.
– Tetracarpellary : It is
presence of four carpels,
• Pentacarpellary : It is presence
of five carpels, e.g., Hibiscus.
• Multicarpellary : It is presence
of many carpels, e.g., Annona.
27. Cohesion of carpel.
If number of carpels is more
than one, they may be
• (i) Apocarpous: Carpels
are free. Each carpel has
its own style and stigma,
• (ii) Syncarpous: Carpels
are united, e.g., Lady’s
28. The ovary encloses one to many chambers called the
locules. Usually the number of locules in a syncarpous
ovary corresponds to the number of carpels.
Sometimes, the number of locules may be doubled.
e.g., in Datura, the gynoecium is bicarpellary
syncarpous with four locules in the ovary. Based on the
number of locules, the ovary may be described as
Unilocular : Ovary with one locule. e.g., Dolichos.
Bilocular : Ovary with two locules. e.g., Solanum.
Trilocular : Ovary with three locules. e.g., Allium.
Tetralocular : Ovary with four locules. e.g., Datura.
Pentalocular : Ovary with five locules. e.g., Hibiscus.
Multilocular : Ovary with many locules. e.g., Abutilon.
Placentation refers to the arrangement of ovules
within the ovary. Ovules are attached to ovarian
walls through special structures called as
Marginal: The placenta forms a ridge along
the ventral suture of the ovary and the
ovules are borne on this ridge, e.g., Pea
Axile: The ovary is partitioned into several
chambers or locules and the placentae are
borne along the septa of the ovary, e.g.,
Tomato, China rose
Parietal: The ovules develop on the inner wall
of the ovary or on peripheral part. Ovary
unilocular but in some cases becomes two
chambered due to formation of a false
septum, e.g., Mustard
30. (iv) Free central:
Ovules are borne
on the central axis and
septa are absent, e.g.,
(v) Basal: Placenta
develops at the base of
The stalk like structure present above the
ovary is called the style. The style may be
long (Datura) or short (grasses) or absent
(Papaver). In the family umbelliferae
(Apiaceae) the base of the style is swollen
and forms a structure called stylopodium.
There are three types of styles as
described below :
32. Kinds of style
Terminal style : If the style
arises from terminal part of
the ovary, it is called
terminal style, e.g., Datura,
Hibiscus and Solanum.
Lateral style : If the style
arises from one side of the
ovary, it is called lateral
style, e.g., mango.
Gynobasic style : If the style
arises from the base of the
ovary it is called gynobasic
style, e.g., Ocimum, Salvia.
The terminal pollen
receptive portion of the
style is called the
It receptive pollen grain
Usually the lobes of the
stigma equal to the
number of carpels.
The stigma may be unifid,
bifid, trifid, tetrafid,
pentafid or multifid.
35. FLORAL FORMULA
• Once the description of the plant is completed,
major characters of the flower are written in a
special method where few signs and letters are
• This formula is useful in knowing major
characters of a flower at a glance. In this method
characters of bracts, symmetry sex, calyx,
corolla, (or parianth), androecium and
gynoecium are denoted in this order. Some of
the commonly used denotations are given
38. • Androecium;
A5……..Five free stamens
A(5)……Five fused stamen.
A5+5…..Ten stamen in two
whorl of five each
indefinite in number.
C A… .. Stamens
P A…… Staens epiphyllous
G3……….three free carpels
G0……….. Carpels absent
G_(2)……..two fused carpel,
G(3) ………Three fused
carpel, semi inferior overy.
carpel, inferior overy.
41. Floral diagram
• Floral Diagram
• The floral diagram is a ideal ground plan of a
flower. It is a method in which many of the
characteristics of its parts and symmetry can be
expressed in a graphic form.
42. Insertion of floral leaves
It means the structure of thalamus and the consequent position and
insertion of calyx, corolla and androecium in relation to the pistil
• A flower in which the
overy is superior and all
other floral organs are
situated below its level.
43. • Perigynous:
• The thalamus is flat or concave and the floral
organs arising from around the ovary and not
beneath it. Papilionaceae
44. • Epigynous:
• The thalamus is concave and the floral member
are arise above the pistil. E.g. Compositae
46. Flower is Modified shoot
• Morphologically a flower is a modified
shoot. The elongated axis (internodes) of
a vegetative shoot is reduced into a
horizontal disc, the receptacle. Floral
leaves are arranged on the receptacle in
• By the Following fact it can be established
that the flower is modified shoot.
47. 1. Axis nature of the thalamus: Flower consists of a
thalamus or torus, which is very much like an axis in some
• a. The axis bears modified floral leaves such as
sepals, petals, stamens and carpels. Generally the
axis in a flower consist of short or suppressed
Internodes and nodes. But it is not the normal rule;
the axis is long in some flower e.g. Gynandropsis
gynandra ( Capparidaceae ), Passiflora suberosa (
Passifloraceae) etc. The internode of the thallamus
between corolla and androecium (andophore) and
between androecium and gynoecium (gynoephore)
become enlarged with same whorled arrangement of
stamens and carpels respectively.; so here thalamus
behaves like a axile.
49. • b. Normally the growth of the thalamus is
checked by the carpels but in some the
thalamus has been found to undergo
further upward growth having green stem
and small foliage leaves beyond the
gynoecium, this phenomenon also support
that flower is a modified shoot. E.g. Rosa
sp, Pyrus sp This phenomenon is known
as monstrous development.
50. • c. In some cases the carpel bearing region
of the thalamus elongate like the stem
giving rise to an aggregate fruit. E.g.
Polyalthia longifolia Michalia champaca
51. 2. Leaf nature of floral member: This is evident
by many plant member Following are some
a. In many cases the
sepal are leaf like
with veins and
e.g Mussanda frondosa
52. b. In some cases the floral leaves are both
verticillately and spirally arranged On long
thalamus but in majority of flowers the floral
phyllotaxy is whorled eg Michalia champaca
c. The leaf nature is also proved by the gradual
transition of sepals to petals and petals to
stamen and so on as in found in Nymphaea
53. D. Carpel is also leafy in nature can
be proved by on examination of
single carpel of Pisum sativum
in which it is folded along its
midrib to form a chamber.
54. 3. Homology of floral buds
Floral buds like vegetative buds may be
metamorphosed bulbils e.g. viviparous
bulbils of Agava sp. Development and
position of vegetative bud are also like
those of floral buds i.e. axillary and