湖南桦木科植物的研究

湖南桦木科植物有5属22种7变种，分布于27个县，多生长在海拔800－1600m的山地阔叶林中．本文依据湖南桦本科植物的分类学研究，结合地理分布和植物区系资料，经分析和推论得知：1．湖南桦木科植物种质资源比较丰富，以中国特有成份为主，它们与毗邻地区种类的关系密切．2．湖南桦水科植物区系表现为多种区系成份的过渡与汇集，即华中、滇黔桂、华南和华东四个区系成份的交汇、混杂和过渡．3．湖南桦本科的多数植物是从湘西北以外地区迁移扩散而来，一些植物是从湖南西部至西南部以外地区迁移扩散而来，极少数植物是在湘西北或湘西南地区分化形成．4．湘西北地区是湖南桦本科植物的第一现代分布中心和现代分化中心，湘西南地区是第二现代分布中心和现代分化中心．

STUDY ON THE BETULACEAE FAMILY IN HUNAN

There are 5 genera,22 species and 7 varieties of the Betulaceae family in Hunan province. These plants are distributed in 27 counties,and maily grow in the broad-leaved forests on the mountains of an altitude of from 800 to 1600 metres.According to the evidence of systematics of the family,and with reference to the material of distribution and flora,the paper condudes as follows: (1 )The species of Betulaceae are rich in Hunan. Most of the species are endemic to China,and closely related to those in neighbouring regions. (2)The flora of Betulaceae in Hunan is accompanied by transition and convergent features of different floristic elements, especially between the floras of Central China and Yunnan,Guizhou and Guangxi,as well as between the floras of South China and East China. (3)Most of the species of Betulaceae in Hunan were from the northwest regions of Hunan, some species were from the regions from west to southwest of Hunan,a few species were differentiated and formed in the northwest or southwest of Hunan. (4)The first centre of modern distribution and differentiation of Betulaceae in Hunan is in the northwest of Hunn,and the second centre of modern distribution and differentiation of Betulaceae in Hunan is in the southwest of Hunan.