Preface Acknowledgements A List of Plates Ⅰ Hybrido-embryology in Populus 1 Development of sex organs 1.1 Flowers and inflorescences 1.2 Floral morphology 1.3 Development of pollen 1.4 Development of embryo sac 1.5 Summary 2 The secretory stigma 2.1 Light Microscopy and cytochemistry 2.2 Scanning electron microscopy 2.3 Transmission electron microscopy 2.4 ATPase activities in stigma cells of P.lasiocarpa 2.5 Summary 3 Pollen-stigma Interaction 3.1 Germinated pollen grains and their wall sculptures 3.2 Pollen tube behaviour on stigmas 3.3 Discussion 4 The Progamic Phase 4.1 Conspecific matings 4.2 Intersectional crosses 4.3 Intergeneric cross:P. simonii × Salix matsudana 4.4 Summary 5 Double Fertilization 5.1 Conspecific matings 5.2 Intersectional crosses 5.3 Intergeneric cross: P. simonii × Salix matsudana 5.4 Summary 6 Development of Embryo and Endosperm 6.1 Conspecific matings 6.2 Intersectional crosses 6.3 Intergeneric cross: P. simonii × Salix matsudana 6.4 Summary Ⅱ. Sexual Reproductive biology of Distant Hybridization in Cunninghamia 7 Intergeneric Cross Between Cunninghamia and Cryptomeria 7.1 Controlled pollination and hybrid seed production 7.2 Soft X-ray detection of hybrid seeds 7.3 Seed germination and hybrid seedlings 7.4 PCR and RFLP analysis 7.5 Summary 8 Interfamilial Cross Between Cunninghamia lanceolata and Platycladus orientalis 8.1 Controlled pollination and sample preparation 8.2 Pollen germination and pollen tube growth 8.3 Fertilization and postfertilization 8.4 Summary Ⅲ. Application of Cytobiological Techniques for Overcoming Barriers to Hybridization 9 In ovulo Embryo Culture in Populus 9.1 In ovulo embryo culture for Populus euphratica 9.2 In ovulo embryo culture for intersectional crosses 9.3 Intergeneric cross: P. simonii × S. matsudana 9.4 Summary 10 Isolation of Viable Gametes: Towards in vitro Fertilization 10.1 Angiosperms 10.2 Gymnosperms 10.3 Summary A List of Plates 80