Archesporium is a cell or cell structure in a sporophyte from which spores may later develop during the alternate generation. Archesporium cell divides into the primary parietal cell which later forms the anther wall and primary sporogenous cells which form the microspore mother cell. Primary parietal wall after few more periclinal divisions forms anther wall and sporogenous cells give rise to sporogenous tissue.
Related Theory
The pollen grain grows into the male gametophyte on germination which is initiated before pollination takes place. Inside the microsporangium. Pollen mother cell (PMC) undergoes meiosis and results in four microspores which eventually mature into pollen grains.