Microsporogenesis: The development of microspores from archesporial cells is called microsporogenesis. It takes place in following steps :
(a) A few microspore mother cells disintegrate and are absorbed by remaining spore mother cells.
(b) The microspore mother cells divide meiotically to form microspores.
(c) The division may be of two types either (a) Successive type or (b) Simultaneous type.
(d) In the successive type, each nuclear division is followed by wall formation. Thus, two similar cells are formed and then four. This structure is called isobilateral tetrad.
(e) Contrary to this, in simultaneous type, the division occurs centripetally dividing the cells into four parts. This is called tetrahedral tetrad.