Abstract:As oneofthelargest andpantropical generainthefamily Rubiaceae，the genus Heddyotis L．sensu lato， including subgenera Hedyotis，Oldenlandia and Houstonla，is applied in this paper．They characterized by having tetramerous flowers with valvate corollas and equal calyx lobes，expanded，fleshy，peltate placentae and moderately flattened capsular with selerified endocarps． Basing on the extant literatures，699 species are included in this genus．Tropical Africa and Asia are two modern distribution centers．Endemic species are distributed in all tropical continents．About 68 species(including varieties) growing in S．and SW China．The modern distribution pattern and cytogeography data reveal that：(1)Hedyotis was originated in the Gondwana land before late Jurassic，and might be originated on the amplearea of NE Gondwana land during Jurassic，even in early Triassic;(2) They dispersed in four ways
from the original center：eastward，to SE Asin via Turkey，Iran and S．China，where was the southern areas of the Laurasia land; southeastward，to India and Australia via paleo-antaletie land：northward，to North America via cent1al paleo-pacifie; southwestward，to S．America，which was united with Africa at that time and was also one main part of the Gondwana land．The continantal drift，especially the breakup of Gondwana， slowed down the speed of such dispersal in Jurassic time．Subsequently， the species developed in these separated continents．The global glacier had also ptayed an important role in the present distribution pattern．