Tóm tắt
After the breakup of the meiotic tetrads, it is usual in the Compositae for the cells of the previously parietal tapetum to invade the anther loculus and form a Plasmodium ramifying between the young spores. In species of three tribes, Helenieae, Heliantheae, and Ambrosieae, an extratapetal membrane is formed at this time, which totally encloses the tapetum and the spore mass. The extratapetal membrane is resistant to acetolysis, and is considered to be chemically similar to the sporopollenin of the pollen grain exine.
