The younger elements take the dominant position, the ancient ones are fewer, and the flora occurred and developed progressively along with Himalaya and Liupan Mountain rising in the Third Period.5.

• 4．本区系中年轻成分占较大优势，古老成分很少，植物区系是随第三纪喜马拉雅造山运动及六盘山隆起逐步形成和发展起来的。