In parallel to these developments, the other kind of sporangium, the microsporangium, produces microspores.
From the en.wikipedia.org
Each microsporangium is lined with a nutritive tissue layer called the tapetum and initially contains diploid pollen mother cells.
From the en.wikipedia.org
In some flowering plants, germination of the pollen grain often begins before it leaves the microsporangium, with the generative cell forming the two sperm cells.