Male Gametophyte of Cathaya

There are two prothallial cells in Cathaya, but their formation is different fromthat of the other genera of Pinaceae. A primary prothallial cell is cut off first and the divisionof this cell gives rise to 2 prothallial cells which remain intact in mature pollen grains. 3-celledpollen grains are formed. The interval between polination and fertilization is about 13 months. The two sperms are different in size.