MicrosporogenesisThe pollen sacs represent microsporangia. Thus each antherhas four microsporangia, two in each anther LOBE. These are COVERED by thecommon epidermis of the anther. They contain pollen grains or microspores1.  Very young anther consists of group of activelydividing parenchymatous cells SURROUNDED by a layer of epidermis.
2.   It becomes two lobed; each anther lobe developsinto two microsporangia in its two corners.
3.  In each lobe in the two corners one cell becomesconspicuous from the rest- archesporial cell.
4.  Archesporial cell divides to form an outerparietal cell and an inner sporogeneous cell
5.   Parietal cell divides to form concentric layersof pollen sac wall
6.  The pollen wall externally is made up of ASINGLE layered epidermis. Inner to the epidermis is a single layer of radiallyelongated cells with fibrous thickenings which help in dehiscence. The cells inthe shallow groove between two microsporangia remains thin walled and formstomium. Inner to the endothecium lie three to four layers of thin walled cellsoccur in between which disintegrates in mature anthers. The innermost layer ofcells with DENSE cytoplasm which nourishes developing pollen grains is calledTapetum.
7.      The primary sporogeneous cell divides to producea mass of sporogeneous cell or microscopore mother cell.
8.      Microspore mother cell undergoes meiosis to giverise to four haploid microspores. The microspores are arranged in a cluster offour cells to form tetrad. As the anthers mature and dehydrate, microsporedissociates from each other and form pollen grains. In some microspores do notseparate but together form compound pollen grains.