A typical microsporangium appears circular in outline and is surrounded by four walls:

a. Epidermis: It is the outermost single layer of cell which is protective in nature.

b. Endothecium: It is the second layer with thick cells, help in dehiscence and is protective in nature.

c. Middle layer: It is the third layer composed of 1-3 layers of cells, help in dehiscence and is protective in nature.

d. Tapetum: It is the fourth and innermost layer of cell with dense cytoplasm and many nuclei. It provides nourishment to the developing pollen grains.