Studies on Microspores Development and Male Gametophytes Formation of Ostryopsis davidiana Decne

Ostryopsis davidiana Decne.belongs to the family Betulaceae.In order to further probe the embryological relationships among genera of the family,the development process of its microspores and the formation of male gametophytes were studied in the paper with the normal paraffin sectioning.The results are as follows:O.davidiana approximately experience 6 months from pollen mother cell to mature pollen grain and survive in winter in the form of pollen mother cell.Pollination occurs in middle of April.Anthers are bisporangiate.Anther wall develops according to the basic type,and it consists of epidermis,endothecium,2～3 middle layers,and the tapetum.Tapetum grows according to the glandular type,and then disappears in its original position.Meiosis of pollen mother cells is simultaneous type.Tetrads are tetrahedral.Pollen grains are three-germinating pore and rarely four pores.The wall of germinating pore is not thickened.And most of mature pollen grains are 2-celled,and rarely 3-celled.Compared with Betula platyphylla Suk.,O.davidiana has more stamen number and tetrad trends unitizing.These results indicated that the concept of generalized Betulaceae is more reasonable,Ostryopsis Decne.and Betula L.develop in the different ways and the form in which the family Betulaceae survives in winter can be a new evidence of difference among its genera.