The androecium

The "androecium" refers to all of the stamens in a flower.

A stamen consists of an anther and a filament. The anther has one, two, or four pollen sacs, each containing pollen. The stalk of the anther is the filament. Sterile (nonreproductive) tissue between pollen sacs (an extension of the filament) is called the connective.

Anthers may be connected to the filament at their base (called "basifixed" anthers in most texts) or at their backs (called "dorsifixed" anthers in many texts). In some cases, anthers attached to a filament at their backs can swing freely on their filaments, and are called versatile anthers.

Patterns of anther attachment to filament
Stamens, showing different ways anther sacs attach to filaments. Each stamen here has two anther sacs (or pollen sacs). [Redrawn from Michael G. Simpson's Plant Systematics, 2005).

Anther sacs may dehisce by pores, by longitudinal slits, by transverse slits, or by valves to release pollen grains.

Patterns of anther dehiscence
Patterns of anther dehiscence. [From Michael G. Simpson, 2005, Plant Systematics]

Stamens may have appendages in various locations, and their connective may take on different shapes. Examples are shown below.

Variation in connective and stamen appendages.
Stamen variation. Illustration from A Manual of Structural Botany, 1911, by H.H. Rusby. The stamen labeled "165" has a branched connective and one aborted anther. Appendages on other stamens are indicated with red arrows.

Some flowers have one or more staminodes (sterile stamens or stamens without functional anthers).