Callo Callose wall Callose wall premelocyte MEIOSIS I and‖l Callase from tapetum Generative cell re exine Tetrad MICROSPORE cell nucleus MITOSIS Exi uninucleate microspore 4>enlargement microspore vacuole Free young detachment Microspores vacuolation Uninucleate DEHYDRATION Immature dormant mature pollen grain