Abstract: The initiation and development of flower organs in Catalpa speciosa (Warder) Warder ex Engelm were observed by light microscope and scanning electron microscope. The results showed that: (1) The whole process of floral initiation and development lasted about one month from late March to early May. (2) On the floral apex the different classes of organ primordia appeared in the following sequence: calyx, corolla, androecium and gynoecium, and they had overlapped with each other when occurring in turn. (3) The development of anther and ovule followed the finish of the flower organ initiation. Pollen mother cells and well developed microsporagium wall occurred when the diameter of the bud reached about 3.0 mm, and the archesporial cell which played the role of megaspore mother cell formed in ovule when the diameter of the bud reached about 3.5 mm.

Key words: Catalpa speciosa (Warder) Warder ex Engelm, Bignoniaceae, floral organogenesis and development, morphology and anatomy