This document discusses different types of inflorescences, which are clusters of flowers on a plant. It describes eight main types of racemose inflorescences: raceme, panicle, corymb, spike, spadix, umbel, capitulum, and catkin. For each type, it provides details on the structure of the flower cluster and examples of plant species that exhibit that inflorescence type.

1. Welcome
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2. Inflorescence
Flowers are the organs of sexual reproduction in higher plants.
They are in fact modified shoots
 They may occur either singly (solitary flowers) or in bunches
on a common axis.
 Solitary flowers may be axillary or terminal.
 Axillary flower is a modified axillary bud, and terminal flower is
a modified terminal bud.
 An axis, bearing a bunch of flowers is known as inflorescence.

3.  Inflorescence may be axillary or terminal in position.
 The axial stalk or the main axis of the inflorescence is
called rachis or peduncle.
 The individual flowers of an inflorescence are attached
to the peduncle by stalks of their own, known as the
pedicels.

4.  In some cases, flowers are stalkless and are sessile
flowers, e.g., Achyranthes.
 In some plants like Lotus, and Onion, a long peduncle
arises from the underground stem and bears flowers.
 Such a peduncle is called scape. It may bear a single
flower as in Lotus, or a cluster of flowers as in Onion.
 In Agave, it is branched and the branches bear flowers.

5.  In most plants, pedicel arise from the axil of a very small greenish, or
brownish leaf-like structure on the peduncle, called bract.
 Bracts are highly reduced and modified leaves and their arrangement on
the peduncle is the same as that of leaves on a vegetative shoot.
 When the peduncle is branched, the branches arise from the axils of
similar bracts.
 res are absent, then the flowers are said to be ebracteate and
ebracteolate.

6.  Bracts differ from leaves in some respects, such as colour, size and
shape.
 Besides these bracts, there may be one or two still further reduced bract-
like structures on the pedicel, known as the bracteoles.
 Flowers having bracts and bracteoles are described as bracteate and
brocteolate respectively.
 If these structuare absent, then the flowers are said to be ebracteate and
ebracteolate.

7.  Based on the nature of the peduncle and the arrangement of flowers three
main types of inflorescence can be recognized, namely
Racemose,
Cymose
 and Special.

8. A. Racemose inflorescence
 It is called indefinite, or indeterminate inflorescence.
 In it, the main axis does not end in a flower and is capable of
unlimited (indefinite or indeterminate) growth.

9.  Flowers are arranged on either side of it in acropetal succession.
 Sometimes, the main axis may give rise to a number of branches in
acropetal succession and the flowers are arranged on these branches, in a
similar manner.
 At times, the main axis may become very short and the flowers form a
cluster with the older flowers at the periphery and the youngest one at
centre.


10. Racemose inflorescence is of several
kinds.
 The commonest ones among them
are
 raceme,
 panicle,
 corymb,
 spike,
 spadix,
 umbel,
 capitulum and catkin.

11. I. Raceme
 This is the simplest type of racemose inflorescence.
 It has a main peduncle on which a number of flowers are borne in
acropetal succession.
 All the flowers are pedicellate, e.g, Glyricidia, Crotalaria.

12. II. Panicle
 This is a branched raceme.
 The main peduncle gives rise to a number of secondary peduncles in
acropetal succession and flowers arise on the secondary peduncles in
acropetal succession.
 In yet other instances, secondary peduncles may branch and the
flowers arise on the tertiary peduncles, e.g., mango, teak.

13. III. Corymb
 This is a type of raceme in which the peduncle is very short Habit and it
bears acropetally arranged pedicellate flowers.
 The pedicels of the flowers have different lengths.
 The oldest (basal) flowers have longest pedicels, and the youngest
(terminal) ones have shortest pedicels.
 As a result, all the flowers of the inflorescence stand more or less at the
same level, e.g., Caesalpinia, Gynandropsis.
 In many cases, the main axis of the corymb elongates after flowering so
that the corymb becomes a raceme.

15. III Spike
 This resembles a raceme except for the sessile nature of flowers. e.g.,
Achyranthes, Celosia.
 In some cases, the main axis of the spike is branched, and each branch
resembles a spike.
 Such an inflorescence is called compound spike, e.g., Aerva.
 The small spikes found in grasses are called spikelets.

17. V. Spadix
 This is the racemose inflorescence in which the peduncle is thick, fleshy
and coloured.
 Flowers are small, sessile and unisexual and they sink into the
depressions on the axis, called spodices.
 The whole inflorescence is covered by a leathery bract, called spathe.
 Generally, female flowers are basal and male flowers terminal in position.
Spadix inflorescence is characteristic of monocots. e.g. Colocasia, Cocos,
Areca, Musa, Amorphophallus.
 In Cocos and Areca the inflorescence is branched and the spathe is boat-
like.

20. VI. Umbel
 This is the racemose inflorescence in which the main peduncle is short and
bears at its tip a whorl of bracts.
 From the axil of each bract, arises a pedicellate flower.
 Flowers are arranged in centripetal succession.
 (older flowers towards Pedunclethe margin and younger ones towards
the centre).
 As in corymb, here also all the flowers are at the same level.
 But in corymb, pedicels are of different lengths and start from different
lengths of the peduncle.
 Eg. Biophytum

23.  In umbel, all the pedicels are of equal length and all of them start from the
apex of the peduncle.
 The racemose nature of the inflorescence is evident from the centripetal
arrangement of flowers.
 The main peduncle may be simple, or it may bear a cluster of flowers at
the apex as in onion.
 In compound umbel, the main peduncle may give rise to secondary
peduncles, and pedicels start their tips in an umbellate manner as in
coriander and carrot
 . The whorl of bracts below the cluster of pedicels forms an involucre.

24. VII. Capitulum or head
 This racemose inflorescence is peculiar in that the main peduncle gets
flattened out at the apex into a slightly convex platform-like structure,
called receptacle.
 On the surface of the receptacle numerous small and sessile flowers are
arranged in centripetal succession.
 At the base of the receptacle, there are numerous green and triangular
bracts, which form an involucre.
 The individual flowers on a head inflorescence are called florets.

25.  The florets arranged along the periphery of the receptacle are called ray
florets and those arranged along the centre are called disc florets.
 Ray florets are usually zygomorphic and female, whereas disc florets are
actinomorphic and bisexual.
 In some plants, such as Mimosa, Gomphrena, etc., the receptacle is not
flat, but is a swollen and spherical structure and the flowers are arranged
all over it.
 The whole inflorescence looks like a small badminton ball, and is known as
a globose head.

27. VIII. Catkin or amentum
 Catkin is a pendulous type of inflorescence, similar to spike, with sessile
and unisexual flowers. The axis is thin and weak.
 e.g., Acalypha, Morus, Artocarpus.

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