Androecium

Each anther is usually bilobed and each lobe has two chambers, the pollen-sacs.

The pollen grains are produced in pollen-sacs. A sterile stamen is called staminode

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Aestivation

Valvate :

When sepals or petals in a whorl just touch one another at the margin, without overlapping, as in Calotropis, it is said to be valvate.e.g., Mimosaceae

Twisted :

If one margin of the appendage overlaps that of the next one and so on as in china rose, lady’s finger and cotton, it is called twisted.  e.g., Malvaceae

Imbricate :

If the margins of sepals or petals overlap one another but not in any particular direction as in Cassia and gulmohur, the aestivation is called imbricate. e.g., Caesalppinaaceae

Quincuncial :

the margins of two petals are inside and two petals are outside, and one petal's margin is both inside and outside.  e.g., Apocynaceae

Vexillary :

In pea and bean flowers, there are five petals, the largest (standard) overlaps the two lateral petals (wings) which in turn overlap the two smallest anterior petals (keel)

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Union of stamen

Stamens of flower may be united with other members (adhesion) such as petals or among themselves (cohesion)

Adhesion of stamen

When stamens are attached to the petals, they are epipetalous  e.g., brinjal, Datura (solanaceae)

Adhesion of stamen

when attached to the perianth called epiphyllouse.g., lily (liliaceae), Asperagus (asparagaceae)

Adhesion of stamen

Stamen may unite with gynoecium called gynandrous, it is also called gynandrium or gynostegium' e.g., calotropis (apocynaceae)

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Cohesion of stamens

Adelphous

Anthers remain free, and filaments are united. Adelphous condition can be;

Monadelphous–  The stamens may be united into one bunch or one bundle. e.g., china rose  (malvaceae)

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Adelphous 

Diadelphous– The stamens united to form two bundles. e.g., Pea (Papilionaceae)

Adelphous 

Polydelphous– The stamens united into more than two bundles. e.g., Lemon (Rutaceae)

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Synandrous

Stamens fused all through their length. e.g., Cucurbita 

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