1. College of Horticulture, Jinling Institute of Technology, Nanjing City, P. R. China
2. Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing City, P. R. China
3. Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, Vancouver, Canada