Describe internal structure of anther by mentioning about typical stamen.

Two parts of a typical stamen are shown in the figure below. The long and slender stalk is called the filament and the terminal generally bilobed structure is called the anther. The proximal end of the filament is attached to the thalamus or the petal of the flower. The number and length of stamens are variable in flowers of different species.

Collecting a stamen each from ten flowers the large variation in size is seen in nature. Careful observation of each stamen under a dissecting microscope elucidate the range in shape and attachment of anthers in different flowers.

$(a)$ A typical stamen $(b)$ three-dimensional cut section of an anther

A typical angiosperm anther is bilobed with each lobe having two theca, i.e. they are dithecous.

Often a longitudinal groove runs lengthwise separating the theca. Anther consists of four microsporangia located at the corners.

The microsporangia develop further and become pollen sacs.

Pollen sacs are packed with pollen grains.