Tetrad Lilium grandiflorum Petunia hybrida Tetrad (Gr tetra = four) is the name given to the period within post-meiostic differentiation during which the four microspores (sometimes also the megaspores) are still together. They are only separated by a temporary cell wall.

http://www.vcbio.science.ru.nl/en/virtuallessons/cellcycle/postmeio/tetrad/print/