Fig. 13

a, b, c are stage A, stage B, and stage C, respectively. 1 to 6 were different sporangial developmental phases in stage A.1: Enclosing sporangial initials in parietal cells, mononuclear and binuclear sporangial initials can be seen.2: Sporangial initial divided into outer tapetum cells and inner spore mother cells.3: The spore mother cells undergo the first meiosis.4: The two cells changed from mononuclear to binuclear.5: The two-cell binucleate divided into four-cells. At this time, the tapetum cells were darker and still visible.6: The four-cells divide into 8 cells and tapetum cells disintegrate gradually