In Vitro Rapid Propagation System and in Vitro Germplasm Peservation of Rhododendron schlippenbachii Maxim. Study on in vitro Rapid Propagation of the Hybrid of Bambusa pervariabilis×Dendrocalamus latiflorus No.7 Study on Tissue Culture of Dendrocalamus sinicus Rapid propagation in a Tibetan medicine--Przewalskia tangutica