Arrange the following wall layers of microsporangium starting from outer to inner.

(A) Tapetum
(B) Endothecium
(C) Middle layer
(D) Epidermis

Choose the correct answer from the options given below:

(D), (B), (C), (A)

The correct answer is Option (2) → (D), (B), (C), (A)  

(D) Epidermis

(B) Endothecium

(C) Middle layers

(A) Tapetum

Atypical stamen has two parts – the long and slender stalk called the filament, and the terminal generally bilobed structure called the anther. The anther is a four-sided (tetragonal) structure consisting of four microsporangia located at the corners, two in each lobe.
The microsporangia develop further and become pollen sacs. They extend longitudinally all through the length of an anther and are packed with pollen grains. In a transverse section, a typical microsporangium appears near circular in outline. It is generally surrounded by four wall layers– the epidermis, endothecium, middle layers and the tapetum. The outer three wall layers perform the function of protection and help in dehiscence of anther to release the pollen. The innermost wall layer is the tapetum. It nourishes the developing pollen grains.