中文摘要：

云南南部与东南部热带地区在地理上接近,具有类似的热带季风气候和热带雨林植被,它们的植物区系均以热带成分占优势,在现代植物区系分区上都属于热带亚洲或印度—马来西亚植物区系。研究发现在云南东南部植物区系中具有丰富的东亚植物区系的代表成分,如木兰科、山茱萸科、菝葜科、茶科、安息香科、山矾科、忍冬科、冬青科、卫矛科等,意味着它具有东亚植物区系起源背景,而在云南南部植物区系中却有丰富的热带亚洲代表成分,如楝科、番荔枝科、防己科、姜科、夹竹桃科、萝摩科等,具有明显热带亚洲亲缘。云南南部植物区系中有237个属未见于云南东南部热带地区;云南东南部热带植物区系中有349个属未见于云南南部,包括57个东亚分布属,53个北温带分布属,22个中国特有分布属及17个东亚—北美间断分布属。这些事实意味着云南南部植物区系与东南部植物区系可能具有不同的起源背景,在云南南部与东南部之间可能存在一条历史生物地理线,这条生物地理线暂命名为＂华线（Hua line）＂,它的位置与走向大致与云南的李仙江一致,这些建议也获得地质历史的支持。

英文摘要：

Adjacent tropical south and southeast Yunnan have a similar monsoon climate and are covered by tropical rain forest vegetation at lowlands.Both of the floras of tropical south and southeast Yunnan have tropical floristic elements comprising a majority（78.3% in south Yunnan and 68.83% in tropical southeast Yunnan）,and those of tropical Asian distribution make up the highest ratio（30.2% of the total genera in south Yunnan and 27.3% in southeast Yunnan）,and both of them belong to Indo-Malaysian flora at northern margin of tropical Asia in present floristic regionalization.However,some temperate East Asian characteristic families,such as Magnoliaceae,Cornaceae,Smilacaceae,Theaceae,Styracaceae,Symplocaceae,Aquifoliaceae,Caprifoliaceae and Celastraceae,etc.are well represented in the flora of tropical southeast Yunnan while tropical Asian characteristic families,such as Meliaceae,Annonaceae,Menispermaceae,Zingiberaceae,Apocynaceae,Asclepiadaceae,etc.are well represented in the flora of south Yunnan.Although the tropical south and southeast Yunnan share 80% of their genera,237 genera are seen only in south Yunnan,and 349 genera only in tropical southeast Yunnan respectively.Furthermore,57 genera of East Asia distribution,53 genera of North temperate distribution and 22 genera of endemic to China,as well as 17 genera of East Asia and North America disjonct distribution are present only in tropical southeast Yunnan.These suggest that the flora of southeast Yunnan could have different background from the flora of south Yunnan in origin.The flora of tropical southeast Yunnan is more related to Eastern Asian flora in origin,while the flora of south Yunnan is more related to Indo-Malaysia flora.It is therefore suggested that there could be a biogeographical line between south and southeast Yunnan.The possible biogeographical line is here named as ＂Hua line＂.The biogeographical line is well supported by geological history of the region.