The analysis on the tropical geographical elements of the seed plant flora in the Qinling Mt.

The tropical geographical elements of the flora about of the seed plant in the Qinling Mt.is studied in this paper.The tropical geographical elements in this area belong to 6 categories,such as Pantropic,Tropical America and tropical Asia disjuncted,Old World tropics,Tropical Asia to tropical Australasia,Tropical Asia to tropical Africa and Tropical Asia (Indo Malesia) ect.There are 283 genera,648 species in Qinling Mt.,They make up 30.27 per cent of the total genera and 18.80 per cent of the total species.The dominant element of the tropical geographical composition is the Pantropic and there are 125 genera in this mountain.It makes up 44.17 per cent of all tropical elements.From the quantity component,geographical distribution,characteristics and the phytocoenology function of the tropical geographical elements,the nature of the flora in Qinling Mt.is temperate.The tropical geographical elements are only on the subordinate status,and they distribute in low elevation sector or on the southern side of Qinling Mt.,Some genera of the tropical elements distribute in subtropical,some in the north temperate.This phenomenon shows the transition of the geographical elements of the flora is very obvious.But the origin of the flora in Qinling Mt.has the clear tropical nature.