Multiple choice The innermost wall layer of microsporangium is known as __________. endothecium endodermis tapetum epidermis none of the above Reveal answer Fill a bubble to check yourself C Correct answer Explanation Microsporangium is generally surrounded by four wall layers, the epidermis, endothecium, middle layers and the tapetum (from outer to inner surface). The innermost wall layer is the tapetum.