Pollen (microsporocyte, pollen mother cell or meiocyte), after meiotic division. After the formation of the four microspores, which are contained by callose walls, the development of the pollen grain walls begins. The callose wall is broken down by an enzyme called callase and the freed pollen grains grow in size and develop their characteristic shape and form a resistant outer wall called the exine and an inner wall called the intine. The exine is what is preserved in the fossil record. Two basic types of microsporogenesis are recognised, simultaneous and successive. In simultaneous microsporogenesis meiotic steps I and II are completed
Dehiscence (botany) Dehiscence (botany) Dehiscence is the splitting along a built-in line of weakness in a plant structure in order to release its contents, and is common among fruits, anthers and sporangia. Sometimes this involves the complete detachment of a part. Structures that open in this way are said to be dehiscent. Structures that do not open in this way are called indehiscent, and rely on other mechanisms such as decay or predation to release the contents. A similar process to dehiscence occurs in some flower buds (e.g., "Platycodon", "Fuchsia"), but this is rarely referred to as dehiscence unless circumscissile dehiscence is