Abstract:Pollen tube growth in the ovary of Phaius tankervilliae （Aiton） BI. （Orchidaceae） as observed under scanning electron microscope could be divided into three stages. In first stage, from the beginning ofpoUination to megaspore tetrad, pollen tubes grow axially, passing through gynostemium to the ovary and from proximal placenta along ovary wall develop upward. In second stage, after 2-nucleate embryo sac development, most pollen tubes grow radially around ovules. In third stage, at maturing of the embryo sac, pollen tubes grow directionally toward micropyle into embryo sac. It is suggested that directional growth of pollen tubes are controlled by molecular signal in ovule.
