The parts of a flower are androecium, gynoecium and placentation which are explained below:
Androecium
Androecium is the third and male whorl of the flower and is made up of one or more stamens or microsporophylls. Each stamen has 3 parts
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(a) Filament : lower thread like part of stamen is called filament. It may be absent in some stamens.
(b) Anther : This is the upper swollen part of stamen usually having two lobes (or theca) (in Malvaceae family it has only one lobe or theca). Each lobe contains 2 microsporangia. The two lobed anther is called dithecous anther. Anther with one lobe is called monothecous. The theca are filled with pollen grains (microspores). That part of anther to which connective is attached is considered as the back side of anther and the other side called face usually have longitudinal slits for dispersal of pollen grains. When the face of anther is towards centre of flower it is called introrse e.g., tomato, when it is towards the periphery it is called extrorse e.g.. Ranunculus.
(c) Connective : The filament of the stamen is extended in between the two anther lobes(equivalent to midrib of lamina) and is called connective. In most anthers it is not very prominent but in Salvia it forms long curved structure to one end of which is attached a fertile anther lobe and to the other a knoblike sterile lobe.
Gynoecium (= Pistil)
Gynoecium (= pistil) is made up of one or more carpels (megasporophyllus). Each gynoecium is differentiated into three parts (a) the lower swollen part containing ovules the ovary, (b) elongated thread like structure attached to the apex of the ovary, the style, (c) the tip of the style, the stigma.
The gynoecium may be monocarpellary (made up of one carpel only) or multicarpellary (made up of many carpels). When the number of carpels in a gynoecium are two or more, they may be free or united. If they are free it is called apocarpous gynoecium if they are fused it is called syncarpous gynoecium. Syncarpous gynoecium may be bicarpellary, tricarpellary, tetracarpellary, pentacarpellary or multi-carpellary (if number of carpels exceeds five).
Sometimes the ovary has one chamber (locule), such ovary is called unilocular ovary but sometimes the ovary may be divided into several chambers (locules) e.g., may be bilocular, trilocular, tetralocular, pentalocular or multilocular depending upon the number of locules in the ovary.
The three stigmas of Crocus sativus when dried, form saffron (zafran) of commerce.
Placentation
The ovules are attached on the inner surface of the ovary walls on one or more cushions called placenta. The manner in which placenta (placentae) are arranged on the ovary wall is known as placentation.
Types of placentation :
1. Marginal : In the monocarpellary (Pea) or each carpel of multicarpellary apocarporous (Ranunculus) gynoecium, there is single placenta which develops along the junction of two fused margins.
2. Parietal : When the gynoecium is formed by the fusion of two or more carpels by their adjacent margins, the ovary is unilocular and has two or more longitudinal placenta e.g., Cucurbita, Mustard, Argemone.
3. Axile ; In a multicarpellary syncarpous gynoecium the fusing margins grow inwards to meet in the center of the ovary to form an axis thus making the ovary multichambered (multilocular). The ovules are borne on the central axis e.g., Solanum, China rose.
4. Free central : The ovary is unilocular and the ovules are borne on the axis in the center of the ovary e.g., Dianthus.
5. Basal : The ovary is unilocular and a single ovule is borne at the base of ovary e.g., Sunflower.
6. Superficial : The gynoecium is multicarpellary syncarpous and large number of ovules are borne on the walls of loculi without specific order e.g., Nymphaea (Water lily).