Which one of the following statements is correct?

A typical microsporangium is generally surrounded by four wall layers – the epidermis, endothecium, middle layers and the tapetum. The innermost wall layer is the tapetum. It nourishes the developing pollen grains. Cells of the tapetum possess dense cytoplasm and generally have more than one nucleus. 

The outer three wall layers perform the function of protection and help in dehiscence of anther to release the pollen. 

Endothecium is responsible for dehiscence of anther and release of pollen grains.

Pollen grains have a prominent two-layered wall. The hard-outer layer called the exine is made up of sporopollenin which is one of the most resistant organic material known. The inner wall of the pollen grain is called the intine. It is a thin and continuous layer made up of cellulose and pectin.

When the anther is young, a group of compactly arranged homogenous cells called the sporogenous tissue occupies the centre of each  microsporangium. Cells of sporogenous tissue are diploid (2n).